I've just noticed this bug when i'm trying to share my post with another user in the forum.
Example permalink: http://xenforo.com/community/threads/multi-page-navigation-enhancement.116/page-3#post-56250
This is my post (suggestion) about "Mulit Page Navigation Enhancement" and as you can see from the URL there is a "page-3" part which should be a must for the permalink. Without that part i can't access my post.
Test case: If my message moves back to page-2 my old permalinks won't work as it is stated with it's actual page in that date.
Possible solution: Permalinks should be accessible with only post number.
New permalink: http://xenforo.com/community/threads/multi-page-navigation-enhancement.116/post-56250