It should be a comment for preference. If it doesn't have a firm answer or suggestion then it's effectively discussion. It may well allow another user to bounce off it and create a genuine answer, but the best place is in a comment. If it's a good one, it can still be up voted as a great comment.
The only problem with using a comment is the lack of newline ability, and the fact that there is a character limit. I have on occasion posted what I new to be too long for a comment even though that's what it was as a question, but I put a proviso explaining that at the top asking people not to vote on it. Technically, that's not really a good thing to do, but the guy needed some help reading between the lines.