It is possible to post a question and reply and mark our own post as answer and this behavior might be abusive meaning someone could just post a question and reply and mark as answer to increase number of answered questions and when we observe a profile with several mark as answer posts, we trust the profile. Many forums prevent poster from marking their own post as answer and I believe this is a missing feature in this forum. So those who posted a question shouldn't be able to mark their own post as answer. In this case, forum owner or moderator will be able to mark as answer when they believe it is a real answer.