This question already has an answer here:
From the title, I imagine the obvious reaction would be "No, posting someone else's answer as your own is stealing," at least to me. But the question I'm looking at is interesting: someone left an answer as a comment, and then the OP posted that as an answer. It was clearly attributed, but even so I would have asked the person who left the comment before posting an answer, even if it was my own post. What is the etiquette here?