When I believe that an answer I put forth should be accepted, I report it as "my answer should be accepted." I have received about 20 e-mails saying "You suggested... it is now accepted. Thanks for your contributions!"
If you're not sure if it is a mistake or not the discussions are a good place to bring it up and hopefully someone will either confirm what you thought, or else explain it to you. If you know it's wrong though, reporting it is what you should do.