[wp-hackers] comment_form_title not working with threaded comments

[RePost]

This tag is supposed to display "Reply to (author)," but it's not 
working for me and others who have posted on the WordPress forums 
without  finding a solution.

Here's the way I coded the tag:
<?php comment_form_title( 'Add <em>your</em> comment', 'Reply to %s' ); ?>

"Add your comment" displays every time, even when the poster is replying 
to another comment.

Site link:
http://bit.ly/DBe8x

Background on this issue:

Thread:
http://wordpress.org/support/topic/225225?replies=8#post-1095665

Ticket opened; immediately closed:
http://core.trac.wordpress.org/ticket/8639