diff --git a/bower.json b/bower.json
index 6abd2b2f..14a1176e 100644
--- a/bower.json
+++ b/bower.json
@@ -25,6 +25,7 @@
     "yaml.js": "https://github.com/jeremyfa/yaml.js.git#~0.1.4",
     "stackedit-pagedown": "https://github.com/benweet/stackedit-pagedown.git#d81b3689a99c84832d8885f607e6de860fb7d94a",
     "prism": "gh-pages",
-    "MutationObservers": "https://github.com/Polymer/MutationObservers.git#~0.2.1"
+    "MutationObservers": "https://github.com/Polymer/MutationObservers.git#~0.2.1",
+    "rangy": "~1.2.3"
   }
 }
diff --git a/public/res/editor.js b/public/res/editor.js
index 91a5cc30..aa8c0d9e 100644
--- a/public/res/editor.js
+++ b/public/res/editor.js
@@ -62,7 +62,9 @@ define([
     });
 
     function saveEditorState() {
-        setTimeout
+        if(!inputElt.focused) {
+            return;
+        }
         selectionStart = inputElt.selectionStart;
         selectionEnd = inputElt.selectionEnd;
         scrollTop = inputElt.scrollTop;
@@ -106,6 +108,7 @@ define([
     var cursorY = 0;
     function saveCursorCoordinates() {
         saveEditorState();
+        $inputElt.toggleClass('has-selection', selectionStart !== selectionEnd);
 
         var backwards = false;
         var selection = window.getSelection();
@@ -129,10 +132,10 @@ define([
             var cursorOffset = backwards ? selectionStart : selectionEnd;
             var selectedChar = inputElt.textContent[cursorOffset];
             if(selectedChar === undefined || selectedChar == '\n') {
-                selectionRange = createRange(cursorOffset - 1, cursorOffset);
+                selectionRange = inputElt.createRange(cursorOffset - 1, cursorOffset);
             }
             else {
-                selectionRange = createRange(cursorOffset, cursorOffset + 1);
+                selectionRange = inputElt.createRange(cursorOffset, cursorOffset + 1);
             }
             var selectionRect = selectionRange.getBoundingClientRect();
             cursorY = selectionRect.top + selectionRect.height / 2 - inputElt.offsetTop + inputElt.scrollTop;
@@ -195,7 +198,7 @@ define([
 
         inputElt.focus = function() {
             editor.$contentElt.focus();
-            this.setSelectionRange(selectionStart, selectionEnd);
+            this.setSelectionStartEnd(selectionStart, selectionEnd);
             inputElt.scrollTop = scrollTop;
         };
         editor.$contentElt.focus(function() {
@@ -234,7 +237,7 @@ define([
                 var replacementText = value.substring(startIndex, value.length - endIndex + 1);
                 endIndex = currentValue.length - endIndex + 1;
 
-                var range = createRange(startIndex, endIndex);
+                var range = inputElt.createRange(startIndex, endIndex);
                 range.deleteContents();
                 range.insertNode(document.createTextNode(replacementText));
             }
@@ -270,7 +273,7 @@ define([
                 }
             },
             set: function (value) {
-                inputElt.setSelectionRange(value, selectionEnd);
+                inputElt.setSelectionStartEnd(value, selectionEnd);
             },
 
             enumerable: true,
@@ -288,23 +291,103 @@ define([
                 }
             },
             set: function (value) {
-                inputElt.setSelectionRange(selectionStart, value);
+                inputElt.setSelectionStartEnd(selectionStart, value);
             },
 
             enumerable: true,
             configurable: true
         });
 
-        inputElt.setSelectionRange = function (ss, se) {
+        inputElt.setSelectionStartEnd = function (ss, se) {
             selectionStart = ss;
             selectionEnd = se;
-            var range = createRange(ss, se);
+            var range = inputElt.createRange(ss, se);
 
             var selection = window.getSelection();
             selection.removeAllRanges();
             selection.addRange(range);
         };
 
+        inputElt.getSelectionStartEnd = function () {
+            return {
+                selectionStart: selectionStart,
+                selectionEnd: selectionEnd
+            }
+        };
+
+        inputElt.createRange = function(ss, se) {
+            function findOffset(ss) {
+                var offset = 0,
+                    element = editor.contentElt,
+                    container;
+
+                do {
+                    container = element;
+                    element = element.firstChild;
+
+                    if (element) {
+                        do {
+                            var len = element.textContent.length;
+
+                            if (offset <= ss && offset + len > ss) {
+                                break;
+                            }
+
+                            offset += len;
+                        } while (element = element.nextSibling);
+                    }
+
+                    if (!element) {
+                        // It's the container's lastChild
+                        break;
+                    }
+                } while (element && element.hasChildNodes() && element.nodeType != 3);
+
+                if (element) {
+                    return {
+                        element: element,
+                        offset: ss - offset
+                    };
+                } else if (container) {
+                    element = container;
+
+                    while (element && element.lastChild) {
+                        element = element.lastChild;
+                    }
+
+                    if (element.nodeType === 3) {
+                        return {
+                            element: element,
+                            offset: element.textContent.length
+                        };
+                    } else {
+                        return {
+                            element: element,
+                            offset: 0
+                        };
+                    }
+                }
+
+                return {
+                    element: editor.contentElt,
+                    offset: 0,
+                    error: true
+                };
+            }
+
+            var range = document.createRange(),
+                offset = findOffset(ss);
+
+            range.setStart(offset.element, offset.offset);
+
+            if (se && se != ss) {
+                offset = findOffset(se);
+            }
+
+            range.setEnd(offset.element, offset.offset);
+            return range;
+        };
+
         var clearNewline = false;
         editor.$contentElt.on('keydown', function (evt) {
             if(
@@ -338,7 +421,11 @@ define([
                 clearNewline = false;
             }
         })
-        .on('mouseup', saveCursorCoordinates)
+        .on('mouseup', function() {
+            setTimeout(function() {
+                saveCursorCoordinates();
+            }, 0);
+        })
         .on('paste', function () {
             pagedownEditor.undoManager.setMode("paste");
             adjustCursorPosition();
@@ -364,7 +451,7 @@ define([
 
             actions[action](state, options);
             inputElt.value = state.before + state.selection + state.after;
-            inputElt.setSelectionRange(state.ss, state.se);
+            inputElt.setSelectionStartEnd(state.ss, state.se);
             $inputElt.trigger('input');
         };
 
@@ -508,7 +595,7 @@ define([
         if(fileChanged === true) {
             editor.contentElt.innerHTML = '';
             editor.contentElt.appendChild(newSectionEltList);
-            inputElt.setSelectionRange(selectionStart, selectionEnd);
+            inputElt.setSelectionStartEnd(selectionStart, selectionEnd);
         }
         else {
             // Remove outdated sections
@@ -536,7 +623,7 @@ define([
                 childNode = nextNode;
             }
 
-            inputElt.setSelectionRange(selectionStart, selectionEnd);
+            inputElt.setSelectionStartEnd(selectionStart, selectionEnd);
         }
     }
 
@@ -559,79 +646,5 @@ define([
         section.highlightedContent = sectionElt;
     }
 
-
-    function createRange(ss, se) {
-        function findOffset(ss) {
-            var offset = 0,
-                element = editor.contentElt,
-                container;
-
-            do {
-                container = element;
-                element = element.firstChild;
-
-                if (element) {
-                    do {
-                        var len = element.textContent.length;
-
-                        if (offset <= ss && offset + len > ss) {
-                            break;
-                        }
-
-                        offset += len;
-                    } while (element = element.nextSibling);
-                }
-
-                if (!element) {
-                    // It's the container's lastChild
-                    break;
-                }
-            } while (element && element.hasChildNodes() && element.nodeType != 3);
-
-            if (element) {
-                return {
-                    element: element,
-                    offset: ss - offset
-                };
-            } else if (container) {
-                element = container;
-
-                while (element && element.lastChild) {
-                    element = element.lastChild;
-                }
-
-                if (element.nodeType === 3) {
-                    return {
-                        element: element,
-                        offset: element.textContent.length
-                    };
-                } else {
-                    return {
-                        element: element,
-                        offset: 0
-                    };
-                }
-            }
-
-            return {
-                element: editor.contentElt,
-                offset: 0,
-                error: true
-            };
-        }
-
-        var range = document.createRange(),
-            offset = findOffset(ss);
-
-        range.setStart(offset.element, offset.offset);
-
-        if (se && se != ss) {
-            offset = findOffset(se);
-        }
-
-        range.setEnd(offset.element, offset.offset);
-        return range;
-    }
-
     return editor;
 });
diff --git a/public/res/extensions/comments.js b/public/res/extensions/comments.js
new file mode 100644
index 00000000..72b1690c
--- /dev/null
+++ b/public/res/extensions/comments.js
@@ -0,0 +1,156 @@
+define([
+    "jquery",
+    "underscore",
+    "utils",
+    "crel",
+    "rangy",
+    "classes/Extension",
+    "text!html/commentsPopoverContent.html",
+    "bootstrap"
+], function($, _, utils, crel, rangy, Extension, commentsPopoverContentHTML) {
+
+    var comments = new Extension("comments", 'Comments');
+
+    var offsetMap = {};
+
+    var inputElt;
+    var marginElt;
+    var newCommentElt = crel('a', {
+        class: 'icon-comment new'
+    });
+    comments.onCursorCoordinates = function(cursorX, cursorY) {
+        var top = (cursorY - 8) + 'px';
+        var right = 10 + 'px';
+        newCommentElt.style.top = top;
+        newCommentElt.style.right = right;
+    };
+
+    var fileDesc;
+    comments.onFileSelected = function(selectedFileDesc) {
+        fileDesc = selectedFileDesc;
+    };
+
+    comments.onReady = function() {
+        var cssApplier = rangy.createCssClassApplier("comment-highlight", {
+            normalize: false
+        });
+        var openedPopover;
+        var selectionRange;
+        var rangyRange;
+        var currentDiscussion;
+
+        inputElt = document.getElementById('wmd-input');
+        marginElt = document.querySelector('#wmd-input > .editor-margin');
+        marginElt.appendChild(newCommentElt);
+        $(document.body).append($('<div class="comments-popover">')).popover({
+            placement: 'auto top',
+            container: '.comments-popover',
+            html: true,
+            title: function() {
+                if(!currentDiscussion) {
+                    return '...';
+                }
+                var titleLength = currentDiscussion.selectionEnd - currentDiscussion.selectionStart;
+                var title = fileDesc.content.substr(currentDiscussion.selectionStart, titleLength > 18 ? 18 : titleLength);
+                if(titleLength > 18) {
+                    title += '...';
+                }
+                return title.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/\u00a0/g, ' ');
+            },
+            content: function() {
+                var content = _.template(commentsPopoverContentHTML, {
+                });
+                return content;
+            },
+            selector: '#wmd-input > .editor-margin > .icon-comment'
+        }).on('show.bs.popover', '#wmd-input > .editor-margin', function(evt) {
+            $(evt.target).addClass('active');
+            inputElt.scrollTop += parseInt(evt.target.style.top) - inputElt.scrollTop - inputElt.offsetHeight * 2/3;
+
+            // Get selected text
+            var inputSelection = inputElt.getSelectionStartEnd();
+            var selectionStart = inputSelection.selectionStart;
+            var selectionEnd = inputSelection.selectionEnd;
+            if(selectionStart === selectionEnd) {
+                var after = inputElt.textContent.substring(selectionStart);
+                var match = /\S+/.exec(after);
+                if(match) {
+                    selectionStart += match.index;
+                    if(match.index === 0) {
+                        while(selectionStart && /\S/.test(inputElt.textContent[selectionStart-1])) {
+                            selectionStart--;
+                        }
+                    }
+                    selectionEnd += match.index + match[0].length;
+                }
+            }
+            selectionRange = inputElt.createRange(selectionStart, selectionEnd);
+            currentDiscussion = {
+                selectionStart: selectionStart,
+                selectionEnd: selectionEnd,
+                comments: []
+            };
+        }).on('shown.bs.popover', '#wmd-input > .editor-margin', function(evt) {
+
+            // Move the popover in the margin
+            var popoverElt = document.querySelector('.comments-popover .popover');
+            var left = -10;
+            if(popoverElt.offsetWidth < marginElt.offsetWidth) {
+                left = marginElt.offsetWidth - popoverElt.offsetWidth - 10;
+            }
+            popoverElt.style.left = left + 'px';
+            popoverElt.querySelector('.arrow').style.left = (marginElt.offsetWidth - parseInt(evt.target.style.right) - evt.target.offsetWidth/2 - left) + 'px';
+
+            var textarea = popoverElt.querySelector('.input-comment-content');
+            $(popoverElt.querySelector('.action-add-comment')).click(function(evt) {
+                var author = utils.getInputTextValue(popoverElt.querySelector('.input-comment-author'));
+                var content = utils.getInputTextValue(textarea, evt);
+                if(evt.isPropagationStopped()) {
+                    return;
+                }
+
+                var fileDiscussions = fileDesc.discussions || {};
+                if(!currentDiscussion.discussionIndex) {
+                    do {
+                        currentDiscussion.discussionIndex = utils.randomString();
+                    } while(_.has(fileDiscussions, currentDiscussion.discussionIndex));
+                }
+                currentDiscussion.push({
+                    author: author,
+                    content: content
+                });
+                openedPopover.popover('toggle').popover('destroy');
+            });
+
+            // Prevent from closing on click inside the popover
+            $(popoverElt).on('click', function(evt) {
+                evt.stopPropagation();
+            });
+            setTimeout(function() {
+                openedPopover = $(evt.target);
+
+                // Highlight selected text
+                rangyRange = rangy.createRange();
+                rangyRange.setStart(selectionRange.startContainer, selectionRange.startOffset);
+                rangyRange.setEnd(selectionRange.endContainer, selectionRange.endOffset);
+                cssApplier.applyToRange(rangyRange);
+
+                // Focus on textarea
+                textarea.focus();
+            }, 10);
+        }).on('hide.bs.popover', '#wmd-input > .editor-margin', function(evt) {
+            $(evt.target).removeClass('active');
+
+            // Remove highlight
+            rangyRange && cssApplier.undoToRange(rangyRange);
+            openedPopover = undefined;
+            rangyRange = undefined;
+            currentDiscussion = undefined;
+        }).on('click', function() {
+            // Close on click outside the popover
+            openedPopover && openedPopover.popover('toggle').popover('destroy');
+        });
+    };
+
+    return comments;
+});
diff --git a/public/res/extensions/scrollLink.js b/public/res/extensions/scrollLink.js
index aa16044d..6b0d995b 100644
--- a/public/res/extensions/scrollLink.js
+++ b/public/res/extensions/scrollLink.js
@@ -195,11 +195,9 @@ define([
     var isPreviewVisible = true;
     function setPreviewHidden() {
         isPreviewVisible = false;
-        console.log(isPreviewVisible);
     }
     function setPreviewVisible() {
         isPreviewVisible = true;
-        console.log(isPreviewVisible);
     }
 
     scrollLink.onLayoutConfigure = function(layoutGlobalConfig) {
diff --git a/public/res/html/commentsPopoverContent.html b/public/res/html/commentsPopoverContent.html
new file mode 100644
index 00000000..190de8c2
--- /dev/null
+++ b/public/res/html/commentsPopoverContent.html
@@ -0,0 +1,9 @@
+<div class="form-horizontal">
+    <div class="form-group">
+        <input class="form-control input-comment-author" placeholder="Anonymous"></input>
+        <textarea class="form-control input-comment-content"></textarea>
+    </div>
+    <div class="form-group text-right">
+        <button class="btn btn-primary action-add-comment">Add</button>
+    </div>
+</div>
diff --git a/public/res/main.js b/public/res/main.js
index 342b6f32..1de71861 100644
--- a/public/res/main.js
+++ b/public/res/main.js
@@ -56,7 +56,9 @@ requirejs.config({
         prism: 'bower-libs/prism/prism',
         'prism-core': 'bower-libs/prism/components/prism-core',
         MutationObservers: 'bower-libs/MutationObservers/MutationObserver',
-        WeakMap: 'bower-libs/WeakMap/weakmap'
+        WeakMap: 'bower-libs/WeakMap/weakmap',
+        rangy: 'bower-libs/rangy/rangy-core',
+        'rangy-cssclassapplier': 'bower-libs/rangy/rangy-cssclassapplier'
     },
     shim: {
         underscore: {
@@ -71,6 +73,12 @@ requirejs.config({
             ],
             exports: 'jQuery.jGrowl'
         },
+        rangy: {
+            exports: 'rangy'
+        },
+        'rangy-cssclassapplier': [
+            'rangy'
+        ],
         mousetrap: {
             exports: 'Mousetrap'
         },
@@ -184,14 +192,16 @@ if (window.baseDir.indexOf('-min') !== -1) {
 
 // RequireJS entry point. By requiring synchronizer, publisher and
 // media-importer, we are actually loading all the modules
-require(["jquery", "core", "eventMgr", "synchronizer", "publisher", "mediaImporter", "css",
-themeModule, ], function($, core, eventMgr) {
+require(["jquery", "rangy", "core", "eventMgr", "synchronizer", "publisher", "mediaImporter", "css", "rangy-cssclassapplier",
+themeModule, ], function($, rangy, core, eventMgr) {
 
     if(window.noStart) {
         return;
     }
 
     $(function() {
+        rangy.init();
+
         // Here, all the modules are loaded and the DOM is ready
         core.onReady();
 
diff --git a/public/res/styles/main.less b/public/res/styles/main.less
index ca76b629..b52424e1 100644
--- a/public/res/styles/main.less
+++ b/public/res/styles/main.less
@@ -152,7 +152,7 @@ body {
 	.user-select(none);
 }
 
-.dropdown-menu, .modal-content, .panel-content, .search-bar {
+.dropdown-menu, .modal-content, .panel-content, .search-bar .popover {
 	.box-shadow(0 4px 12px rgba(0,0,0,.125));
 }
 
@@ -1057,15 +1057,25 @@ a {
         position: absolute;
 		top: 0;
 		.icon-comment {
+			.opacity(0.4);
 			position: absolute;
-			color: fade(@tertiary-color, 12%);
+			color: fade(@tertiary-color, 25%);
 			cursor: pointer;
-			&:hover {
-				color: fade(@tertiary-color, 30%);
+			&:hover, &.active {
+				.opacity(1);
+				color: fade(@tertiary-color, 35%);
 				text-decoration: none;
 			}
 		}
     }
+	&.has-selection > .editor-margin .icon-comment {
+		.opacity(1);
+	}
+
+	.comment-highlight {
+		background-color: fade(@label-danger-bg, 25%);
+		//border-radius: @border-radius-base;
+	}
 
     .code,
     .pre {
@@ -1378,12 +1388,13 @@ input[type="file"] {
 
 .popover {
 	max-width: 350px;
-	padding: 15px;
-	.box-shadow(0 5px 30px rgba(0,0,0,.175));
+	padding: 10px 20px 0;
+	//.box-shadow(0 5px 30px rgba(0,0,0,.175));
 	.popover-title {
 		font-weight: @headings-font-weight;
 		font-size: 24px;
-		padding: 10px 15px;
+		padding: 5px 0 15px;
+		border-bottom: 1px solid @hr-border;
 	}
 	.icon-lock {
         font-size: 38px;
@@ -1392,9 +1403,43 @@ input[type="file"] {
 	.disabled {
 		display: none;
 	}
+	.popover-content {
+		padding-bottom: 0;
+		.btn {
+			padding: 6px 11px;
+		}
+		.input-comment-author {
+			border: none;
+			background: none;
+			.box-shadow(none);
+			font-weight: bold;
+			height: 32px;
+		}
+	}
+
+	.comments-popover & {
+		&.top,
+		&.bottom {
+			.arrow {
+				margin-right: 1px;
+				border-right-width: 0;
+				&:after {
+					margin-left: -11px;
+					border-right-width: 0;
+				}
+			}
+		}
+		&.top .arrow:after {
+			bottom: 2px;
+		}
+		&.bottom .arrow:after {
+			top: 2px;
+		}
+	}
 }
 
 
+
 /********************
  * jGrowl
  ********************/
diff --git a/public/res/themes/original.less b/public/res/themes/original.less
index 7560bf00..60ec923c 100644
--- a/public/res/themes/original.less
+++ b/public/res/themes/original.less
@@ -37,7 +37,7 @@
 	.ace_cursor {
 		border-left-color: #fff;
 	}
-}	
+}
 */
 
 @primary: #9d9d9d;
@@ -73,7 +73,7 @@
 
 
 @tertiary-bg: #fcfcfc;
-@secondary-bg: #f9f9f9;
+@secondary-bg: @tertiary-bg;
 @secondary-bg-light: #f6f6f6;
 @secondary-bg-lighter: @tertiary-bg;
 @secondary-border-color: #e2e2e2;
@@ -93,7 +93,7 @@
     &:hover,
     &:focus,
     &:active,
-    .open &.dropdown-toggle {        
+    .open &.dropdown-toggle {
     	color: #fff;
     }
 }
@@ -125,7 +125,7 @@ a.list-group-item,
 	.ace_cursor {
 		border-left-color: #555;
 	}
-}	
+}
 
 .ui-layout-resizer-north {
 	background-color: fade(@navbar-default-bg, 75%);
@@ -157,4 +157,4 @@ a.list-group-item,
         background-color: @navbar-default-bg;
     }
 }
-*/
\ No newline at end of file
+*/
diff --git a/public/res/utils.js b/public/res/utils.js
index e66334c4..e536753d 100644
--- a/public/res/utils.js
+++ b/public/res/utils.js
@@ -24,7 +24,7 @@ define([
 
     // Transform a selector into a jQuery object
     function jqElt(element) {
-        if(_.isString(element)) {
+        if(_.isString(element) || !element.val) {
             return $(element);
         }
         return element;