It's been a while in Stack Overflow, and I have seen so many times that an actual answer was provided as a comment to the question. Later, I see a list of answers repeating the same thing.
Yes, I know, usually the comment is voted up, however, the poster who actually commented with the perfect answer, ethically waits for OP's reply. And then, what we see is a series of answers on the basis of the previous comments.
The poster providing the correct answer through comment, should be encouraged to post it as an answer when majority of us think so.