diff --git a/codemirror/addon/comment/comment.js b/codemirror/addon/comment/comment.js
new file mode 100644
index 00000000..2dd114d3
--- /dev/null
+++ b/codemirror/addon/comment/comment.js
@@ -0,0 +1,183 @@
+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: http://codemirror.net/LICENSE
+
+(function(mod) {
+  if (typeof exports == "object" && typeof module == "object") // CommonJS
+    mod(require("../../lib/codemirror"));
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror"], mod);
+  else // Plain browser env
+    mod(CodeMirror);
+})(function(CodeMirror) {
+  "use strict";
+
+  var noOptions = {};
+  var nonWS = /[^\s\u00a0]/;
+  var Pos = CodeMirror.Pos;
+
+  function firstNonWS(str) {
+    var found = str.search(nonWS);
+    return found == -1 ? 0 : found;
+  }
+
+  CodeMirror.commands.toggleComment = function(cm) {
+    var minLine = Infinity, ranges = cm.listSelections(), mode = null;
+    for (var i = ranges.length - 1; i >= 0; i--) {
+      var from = ranges[i].from(), to = ranges[i].to();
+      if (from.line >= minLine) continue;
+      if (to.line >= minLine) to = Pos(minLine, 0);
+      minLine = from.line;
+      if (mode == null) {
+        if (cm.uncomment(from, to)) mode = "un";
+        else { cm.lineComment(from, to); mode = "line"; }
+      } else if (mode == "un") {
+        cm.uncomment(from, to);
+      } else {
+        cm.lineComment(from, to);
+      }
+    }
+  };
+
+  CodeMirror.defineExtension("lineComment", function(from, to, options) {
+    if (!options) options = noOptions;
+    var self = this, mode = self.getModeAt(from);
+    var commentString = options.lineComment || mode.lineComment;
+    if (!commentString) {
+      if (options.blockCommentStart || mode.blockCommentStart) {
+        options.fullLines = true;
+        self.blockComment(from, to, options);
+      }
+      return;
+    }
+    var firstLine = self.getLine(from.line);
+    if (firstLine == null) return;
+    var end = Math.min(to.ch != 0 || to.line == from.line ? to.line + 1 : to.line, self.lastLine() + 1);
+    var pad = options.padding == null ? " " : options.padding;
+    var blankLines = options.commentBlankLines || from.line == to.line;
+
+    self.operation(function() {
+      if (options.indent) {
+        var baseString = firstLine.slice(0, firstNonWS(firstLine));
+        for (var i = from.line; i < end; ++i) {
+          var line = self.getLine(i), cut = baseString.length;
+          if (!blankLines && !nonWS.test(line)) continue;
+          if (line.slice(0, cut) != baseString) cut = firstNonWS(line);
+          self.replaceRange(baseString + commentString + pad, Pos(i, 0), Pos(i, cut));
+        }
+      } else {
+        for (var i = from.line; i < end; ++i) {
+          if (blankLines || nonWS.test(self.getLine(i)))
+            self.replaceRange(commentString + pad, Pos(i, 0));
+        }
+      }
+    });
+  });
+
+  CodeMirror.defineExtension("blockComment", function(from, to, options) {
+    if (!options) options = noOptions;
+    var self = this, mode = self.getModeAt(from);
+    var startString = options.blockCommentStart || mode.blockCommentStart;
+    var endString = options.blockCommentEnd || mode.blockCommentEnd;
+    if (!startString || !endString) {
+      if ((options.lineComment || mode.lineComment) && options.fullLines != false)
+        self.lineComment(from, to, options);
+      return;
+    }
+
+    var end = Math.min(to.line, self.lastLine());
+    if (end != from.line && to.ch == 0 && nonWS.test(self.getLine(end))) --end;
+
+    var pad = options.padding == null ? " " : options.padding;
+    if (from.line > end) return;
+
+    self.operation(function() {
+      if (options.fullLines != false) {
+        var lastLineHasText = nonWS.test(self.getLine(end));
+        self.replaceRange(pad + endString, Pos(end));
+        self.replaceRange(startString + pad, Pos(from.line, 0));
+        var lead = options.blockCommentLead || mode.blockCommentLead;
+        if (lead != null) for (var i = from.line + 1; i <= end; ++i)
+          if (i != end || lastLineHasText)
+            self.replaceRange(lead + pad, Pos(i, 0));
+      } else {
+        self.replaceRange(endString, to);
+        self.replaceRange(startString, from);
+      }
+    });
+  });
+
+  CodeMirror.defineExtension("uncomment", function(from, to, options) {
+    if (!options) options = noOptions;
+    var self = this, mode = self.getModeAt(from);
+    var end = Math.min(to.ch != 0 || to.line == from.line ? to.line : to.line - 1, self.lastLine()), start = Math.min(from.line, end);
+
+    // Try finding line comments
+    var lineString = options.lineComment || mode.lineComment, lines = [];
+    var pad = options.padding == null ? " " : options.padding, didSomething;
+    lineComment: {
+      if (!lineString) break lineComment;
+      for (var i = start; i <= end; ++i) {
+        var line = self.getLine(i);
+        var found = line.indexOf(lineString);
+        if (found > -1 && !/comment/.test(self.getTokenTypeAt(Pos(i, found + 1)))) found = -1;
+        if (found == -1 && (i != end || i == start) && nonWS.test(line)) break lineComment;
+        if (found > -1 && nonWS.test(line.slice(0, found))) break lineComment;
+        lines.push(line);
+      }
+      self.operation(function() {
+        for (var i = start; i <= end; ++i) {
+          var line = lines[i - start];
+          var pos = line.indexOf(lineString), endPos = pos + lineString.length;
+          if (pos < 0) continue;
+          if (line.slice(endPos, endPos + pad.length) == pad) endPos += pad.length;
+          didSomething = true;
+          self.replaceRange("", Pos(i, pos), Pos(i, endPos));
+        }
+      });
+      if (didSomething) return true;
+    }
+
+    // Try block comments
+    var startString = options.blockCommentStart || mode.blockCommentStart;
+    var endString = options.blockCommentEnd || mode.blockCommentEnd;
+    if (!startString || !endString) return false;
+    var lead = options.blockCommentLead || mode.blockCommentLead;
+    var startLine = self.getLine(start), endLine = end == start ? startLine : self.getLine(end);
+    var open = startLine.indexOf(startString), close = endLine.lastIndexOf(endString);
+    if (close == -1 && start != end) {
+      endLine = self.getLine(--end);
+      close = endLine.lastIndexOf(endString);
+    }
+    if (open == -1 || close == -1 ||
+        !/comment/.test(self.getTokenTypeAt(Pos(start, open + 1))) ||
+        !/comment/.test(self.getTokenTypeAt(Pos(end, close + 1))))
+      return false;
+
+    // Avoid killing block comments completely outside the selection.
+    // Positions of the last startString before the start of the selection, and the first endString after it.
+    var lastStart = startLine.lastIndexOf(startString, from.ch);
+    var firstEnd = lastStart == -1 ? -1 : startLine.slice(0, from.ch).indexOf(endString, lastStart + startString.length);
+    if (lastStart != -1 && firstEnd != -1 && firstEnd + endString.length != from.ch) return false;
+    // Positions of the first endString after the end of the selection, and the last startString before it.
+    firstEnd = endLine.indexOf(endString, to.ch);
+    var almostLastStart = endLine.slice(to.ch).lastIndexOf(startString, firstEnd - to.ch);
+    lastStart = (firstEnd == -1 || almostLastStart == -1) ? -1 : to.ch + almostLastStart;
+    if (firstEnd != -1 && lastStart != -1 && lastStart != to.ch) return false;
+
+    self.operation(function() {
+      self.replaceRange("", Pos(end, close - (pad && endLine.slice(close - pad.length, close) == pad ? pad.length : 0)),
+                        Pos(end, close + endString.length));
+      var openEnd = open + startString.length;
+      if (pad && startLine.slice(openEnd, openEnd + pad.length) == pad) openEnd += pad.length;
+      self.replaceRange("", Pos(start, open), Pos(start, openEnd));
+      if (lead) for (var i = start + 1; i <= end; ++i) {
+        var line = self.getLine(i), found = line.indexOf(lead);
+        if (found == -1 || nonWS.test(line.slice(0, found))) continue;
+        var foundEnd = found + lead.length;
+        if (pad && line.slice(foundEnd, foundEnd + pad.length) == pad) foundEnd += pad.length;
+        self.replaceRange("", Pos(i, found), Pos(i, foundEnd));
+      }
+    });
+    return true;
+  });
+});
diff --git a/edit.html b/edit.html
index 1d690eb0..351efd6f 100644
--- a/edit.html
+++ b/edit.html
@@ -11,6 +11,7 @@
 		<script src="codemirror/addon/dialog/dialog.js"></script>
 		<script src="codemirror/addon/search/searchcursor.js"></script>
 		<script src="codemirror/addon/search/search.js"></script>
+		<script src="codemirror/addon/comment/comment.js"></script>
 		<script src="codemirror/addon/selection/active-line.js"></script>
 
 		<link rel="stylesheet" href="codemirror/addon/fold/foldgutter.css" />
diff --git a/edit.js b/edit.js
index b5d093be..8a3befc9 100644
--- a/edit.js
+++ b/edit.js
@@ -157,6 +157,9 @@ function initCodeMirror() {
 	CM.commands.nextEditor = function(cm) { nextPrevEditor(cm, 1) };
 	CM.commands.prevEditor = function(cm) { nextPrevEditor(cm, -1) };
 	CM.commands.save = save;
+	CM.commands.blockComment = function(cm) {
+		cm.blockComment(cm.getCursor("from"), cm.getCursor("to"), {fullLines: false});
+	};
 
 	// "basic" keymap only has basic keys by design, so we skip it
 
@@ -178,6 +181,9 @@ function initCodeMirror() {
 		CM.keyMap.emacsy["Alt-/"] = "autocomplete"; // copied from "emacs" keymap
 		// "vim" and "emacs" define their own autocomplete hotkeys
 	}
+	if (!extraKeysCommands.blockComment) {
+		CM.keyMap.sublime["Shift-Ctrl-/"] = "blockComment";
+	}
 
 	if (isWindowsOS) {
 		// "pcDefault" keymap on Windows should have F3/Shift-F3