Questions can be marked as answered, closed or anything like that!!!
We should be able to close the questions and person who answers questions correctly should get rewarded!
We already tag questions with "Solved" and also I've seen [Solved] being added as a prefix to the subject of the thread.
But closing a question for further replies I don't think is a good idea ...
There are some discussions on improving the point scoring system, like allowing user to "thank this user" for the best reply ... but I think that is something for the future :) Also, one question could have more than one correct answer.
Yes. I agree once question could have more than one correct answer. May be we can vote for correct or most appropriate answers.
Q&A forum features is on the long range target list, it's quite a bit of work to make a proper Q&A system, just look at all the work that went into "http://stackoverflow.com/":http://stackoverflow.com/. So once we have progressed on our other feature requests, and gotten "some more people on board":http://developer.qt.nokia.com/blog/view/join_the_team, it's definitely something we want to do.