IMO the "solved" issue can be fixed by using tags. The "Accepted answer" issue can be resolved by using the voting/karma system previously mentioned instead of letting OP select which answer (S)he went with (a la SO), let the votes speak. The one with the most votes, will likely be the best or closest answer.
I may have missed something completely obvious there. Feel free to disagree.
Edit: Not really a feature but more styling on
<code> blocks would be nice. 😉