I personally have never seen a forum where a thread disappears after you have read it, that doesn't make sense to me and I really hate it. Why not just keep the read threads in the "new posts" results??? It's no loss for the people that like the way that it is now, it still shows that the post is read and is still easy to navigate the new posts. However for those that don't like the way it is now it is a real pain. Why would a thread disappear after you have read it?? As I have stated before, many times I, and others, will read a thread, then come back to it a bit later after we think of something to add to the thread. The way it is set up now, the thread disappears and if I want to add to a thread I just won't because I don't want to wade through every forum trying to find the thread I am looking for.
Basically, the new way does not promote posting. It is difficult to find threads to respond to them and that is not what forums are about.