If you think the thread has nothing more to offer you, why don't you just no longer read it?

From a user standpoint there is no difference between a closed thread and a thread you don't click on.

I guess the 2 possible issues are either the few KB it takes up on the servers database for additional useless posts, or you could argue that when you click 'new posts' it is still there and frustrating to ignore, but if either of those 2 issues are bothering you, perhaps your life needs spicing up, or something to create meaning beyond the forums... may i suggest you get a puppy?