Don't replace the classes of forward quotes.

4chan_x.user.js

@@ -3273,7 +3273,7 @@
           _ref = $$('.quotelink', qp);
           for (_i = 0, _len = _ref.length; _i < _len; _i++) {
             quote = _ref[_i];
-            if (quote.hash.slice(1) === replyID) quote.className = 'forwardlink';
+            if (quote.hash.slice(1) === replyID) $.addClass(quote, 'forwardlink');
           }
         }
       } else {

script.coffee

@@ -2658,7 +2658,7 @@ quotePreview =
         replyID = $.x('preceding-sibling::input', @parentNode).name
         for quote in $$ '.quotelink', qp
           if quote.hash[1..] is replyID
-            quote.className = 'forwardlink'
+            $.addClass quote, 'forwardlink'
     else
       qp.textContent = "Loading #{id}..."
       threadID = @pathname.split('/').pop() or $.x('ancestor::div[@class="thread"]', @).firstChild.id