I find the "Unanswered" tab and the "no answers" filter to be rather confusing. Do I understand correctly that the "Unanswered" tab simply refers to questions that may have answers but not a solution accepted by the poster? If so, can they not be renamed "Unsolved"?
A questions counts as unanswered until is has (at least one) answer(s) with positive score or an accepted answer.
We mix semantics of "answered" here; do we mean the OP got an answer, or there is an answer-type post? The naming of the "Unanswered" tab assumes the former meaning which I think is fair.