I have just checked and they are not rewritten for RSS:
'POST_URL' => $viewpost_url . '?' . POST_POST_URL . '=' . $post['post_id'] . '#p' . $post['post_id'],
'FIRST_POST_URL' => $viewpost_url . '?' . POST_POST_URL . '=' . $post['topic_first_post_id'] . '#p' . $post['topic_first_post_id'],
'REPLY_URL' => $replypost_url . '&' . POST_POST_URL . '=' . $post['post_id'],
Honestly I don't know if I should force rewrite even here. As I said I have implemented canonical urls which should avoid creating duplicated content.
If you can convince me (with good reasons) that urls shall be rewritten there as well, I will do.