In our most recent update to http://communityserver.org, we have fixed the issue with "Unanswered Posts". Previously, this filter was really a "no replies" filter, which served a purpose, but was extremely limited.
Perhaps a scenario will help clarify:
Imagine you're a user and you ask a question. Not fast forward an hour, a day, or even a week. You haven't received an answer, so you "bump" the thread. What you don't realize is that since your thread now has a reply, it's no longer classified as "Unanswered". And for anyone that goes thru the unanswered posts looking to help, you've dropped off their radar. :(
With the current fix, if a thread is in a forum that supports the [Un]Answered feature, then we'll leave it in the unanswered queue until you mark the thread as answered. If it's in a forum that doesn't support the feature, then it'll be business as usual.
Hopefully that makes sense...