In theory what Joseph is saying makes sense. When mods delete posts or when the number of posts per page change then the page that a particular post appears on might change. For instance, the previous post by me comes out on page 6 in regular view and on page 7 if I add in the deleted posts (only mods, key masters, and charming princes such as Joseph can see these). If I were to delete a whole bunch of posts before it or change the number of posts then the page that the post appears on might change and the link will no longer be valid.
Edit: After deleting about 25 posts, the page 6 link no longer works.