I am wondering why many answers are posted in the comment section of the question? Why not post as an answer?
I largely agree with everything Hurkyl said. Since people have asked me why I do this let me add a few points.
- When I do this, often it is because I think the question is total turkey shoot. If I foresee no pleasure coming from composing an answer, I try to derive pleasure from teaching the OP (unless the question is dismal to begin with). Dropping an extended hint / sketch is then one of the best options.
- The goal is often to engage the asker. If they don't bite, the question may be on its way out anyway. In the more succesful cases the asker sees the light. Then they may or may not want to post an answer themselves (I often encourage that).
- If somebody feels that the presence of my extended hint/answer-in-a-comment somehow bars them from posting an answer, then... A) I agree 100 per cent with the answerers here - a commenter grants the others the license to use the idea, B) we know who is capable of coming up with a solution to a standard question under their own steam (we can also tell who is plagiarizing), C) if a comment stops a run-of-the-mill answer or three from being posted ... MISSION EFFING ACCOMPLISHED!
(climbing on a soap box)
- We have too many answerers simply reproducing pages or examples from textbooks. I honestly think that we should steer clear from such "answers". Look at my answer in the thread that prompted this complaint. There's nothing in it. It could be straight out of Golomb's book. It probably shows that I wrote that piece out of some sense of duty. My heart wasn't in it. Yes, it paves the way for calculating the period of any binary sequence generated by a linear recurrency relation but... so. Nothing there, just book knowledge. Some of the other answerers that had not studied this topic came up with nice ad hoc ways (orders of matrices and such). All equivalent, and possibly not as readily generalizable, but at least some of them spent a while coming up with their solution.
- More on the same vein. I have come to think that answers that clearly required less than ten minutes of processing from the part of the answerer should be just left unposted. There are a few hit-and-run-operators that make me want to introduce rate limitations for answerers as well. 6 per day, 50 per month is generous enough. Focus on quality, not quantity. The answerers are not sitting in some exam here. After you reached 10k by answering calculus, leave that arena to the noobs, please (unless you can add a genuinely different point of view to that rare question where a new pearl can be found).
If I post an answer in the comments, it is often because it is not, in my opinion, fit to actually be an answer; e.g.
- I feel I need to check it for correctness but am not inclined to do so (e.g. too lazy or busy or uninterested)
- the comment is too tersely stated to make for a good answer, and am not inclined to elaborate more
- I believe a good answer should include more information than I'm inclined to provide
I expect for my comment possibly to be used by someone else who is inclined to write up a proper answer. (and sometimes I even made the comment for that purpose!)
One reason I occasionally do this not mentioned in Hurkyl's or Jyrki Lahtonen's answers is actually for clarification of the question. Specifically, if a question as stated has an overly trivial answer, my assumption is that some condition has been omitted that would make the problem more interesting. I'll usually suggest a possible condition or at least suggest that a condition may be missing in such cases. Pointing out the trivial answer indicates why the question as stated is probably not what the OP intended to ask.
Unfortunately, it often is the case that the trivial answer is the one the OP wanted. I don't make the comment an answer in those cases as, in my opinion, the question would best be deleted entirely at that point. They are virtually always just careless mistakes on the OP's part and have about as much educational value to a third party as would pointing out an arithmetic mistake.