Caught by justdave: comment box <table> was unclosed if you weren't logged in.

template/en/default/bug/edit.html.tmpl

@@ -241,9 +241,9 @@
     <tr>
       <td id="comment_status_commit">
         <!-- The table keeps the commit button aligned with the box. -->
-        <table><tr><td>
         <a name="add_comment"></a>
         [% IF user.id %]
+        <table><tr><td>
           <label for="comment" accesskey="c"><b>Additional <u>C</u>omments</b></label>:
           [% IF Param("insidergroup") && user.in_group(Param("insidergroup")) %]
             <input type="checkbox" name="commentprivacy" value="1"