When you post to a thread (quick reply is the kind that causes the problem, I think) you are automatically subscribed to it- but if you scroll up the page and look at the thread tools, it will say "Subscribe to this thread" - when it should say Unsubscribe etc.
A refresh fixes the problem.
I'm guessing this is a ajax issue?
really, it's only minor, because how many times will you post to a thread then quit it?
titanium_geek