What is the general rule for copy and pasting and posting as answers the exact content of someone's comment? What is required? Credit? Making the post community wiki?
If it is a pure copy-paste of someone else comment, I think one should usually do all three of the below (although I personally do not care much for it being made CW), and at the very least one of them:
Make clear that it is a copy-paste from a comment (this often indirectly achieves 2).
Name the source (this usually does 1 too).
Make it Community Wiki.
Either way I consider reposting a comment-answer as a somewhat of a last resort to avoid effectively answered questions lingering around in the unanswered queue. Thus, I think it is also desirable to wait a bit (a couple hours) before doing such a conversion to allow for genuine answers first; as pointed out in a comment it can also make sense to encourage the original poster of the comment to post their comment, possibly expanded, as an answer before proceeding to repost it.
In my mind the thing to avoid is to come off as somebody trying to grab a few points by deception. If it is made transparent it is a copy-paste everybody can judge for themselves if the vote-up a copy-paste. If it is CW, this is moot, too.
To give explicit credit to the user that said it first is likely a good thing to do and easy enough, but especially for completely routine things I do not consider it as essential either.