If you click on any wiki page in SO, you can find out the versioning history very clearly. Who made the change, what's the comment, source, link, even the very cool difference made with colorful red , green. You can easily know what has been edited. And it's really fast.
Furthermore, when you edit one post, you can choose to rollback the change.
Since some one already asked versioning function, then I change my question to ask how SO manage the workflow function like edit/peer review/approve change/rollback change? I guess it should be belong to workflow functions. I just wonder is there any open source framework can help to do same thing like SO does.
So hope those close votes can be cancelled.