I came across this question and at the time there were no suggested answers. After reading Mark Hubbart's comment (at the time with four upvotes), which was the correct answer, and seeing that it had been over 30 minutes since his comment, I figured I would provide that answer in my own words, which I did. My answer is longer, and I think more rounded and more useful, but the core of the answer came from the comment. I have no idea if I'd have thought up the answer on my own--a definite maybe to that.
Now had I tried to be "honorable" or something, such as instead of answering, suggesting to the commenter that he make his comment an answer, I would only have accomplished giving away easy rep to some other user not as into gratuitous self-denial.
The commenter had merely to enter his comment into an answer box instead of a comment box! It was his choice! Whether he was too lazy or didn't think his answer worthwhile or some other reason is not my responsibility. Must I bend over backward to help him earn points that he so carelessly left lying around for another person to take? It just took a tiny bit of non-laziness on my part to get my text typed into the box that would reward me instead of the box that wouldn't.
If my perspective is incorrect and the community would rather see such answers-as-comments rewarded and supported, I will gladly accept that. In the meantime, I just want to shake off the tiny bit of guilt my overly-nice and overly-concerned-with-propriety self is feeling. :)