Stackoverflow and the associated sites are more or less like that. It sometimes has problems with overzealous users marking tangentially related questions as duplicates but overall it seems to work.

Downvoting costs karma and it's encouraged to give reasons for a downvote. If an answer is outdated a newer answer often quickly rises to the top and often enough the original answerer will promote the better answer. And you can also edit other people's answers and you can see an edit history.

But it only works if there are enough knowledgeable people participating. It's especially bad with new questions because either the question is low quality or the first answer which gets accepted by the questioner right away is bullshit.