I don't know off the top of my head how many posts there are per page, but I'm just going to use 10 for my example.

If a thread exists which already has 10 pages (or a multiple thereof) and someone makes post #11, when the "Post successful" page links back to the thread, it does so to the original page, instead of the new page created by the new post.

Oh, I acknowledge fully I may just be clincally retarded and no one else is getting this.

nope, I've seen that happen in all version of the snitz forum. Forum post page is designed to return you to the page that you where in when you made the post, it's a bit of a pain :/