Unread count real performance improvement. Just like unread.scroll(e), don't update on every nodes.

4chan_x.user.js

@@ -2656,7 +2656,9 @@
       }
       unread.replies.push(root);
       unread.updateTitle();
-      return Favicon.update();
+      if (unread.replies.length === 1) {
+        return Favicon.update();
+      }
     },
     scroll: function(e) {
       var bottom, height, i, reply, _len, _ref;

script.coffee

@@ -1962,7 +1962,8 @@ unread =
     return if root.hidden or root.className
     unread.replies.push root
     unread.updateTitle()
-    Favicon.update()
+    if unread.replies.length is 1
+      Favicon.update()
 
   scroll: (e) ->
     updater.focus = true