I have noticed, of late, people providing answers/copious hints to the question in comments instead of actually adding an answer on their own.
Other people might choose not to answer, as the question has already been answered, and it might offend the person who commented with the answer. In time, this will lead to the site having a lot of questions with 0 answers which actually have an answer in the comments.
Some possible consequences of having answers in comments:
1) Potentially waste time of people. Personally speaking, I read the question before reading the comments, and so I have just wasted a few minutes when I possibly didn't have to. Some people might choose to answer it straight away and find that they have just repeated someone's comment in an answer.
2) The question goes to the unanswered list and they are bumped up periodically by the Community user.
3) Comments are not indexed by the full text search. So we have valuable content just lying around in dead questions.
Here are a couple of examples:
If $f$ continuous and $f(x^2) = f(x)$, then $f$ is a const. This one has an incorrect answer, while the correct answer is in a comment.. The commenter was kind enough to add a detailed answer, upon request.
This problem seems to be more severe with homework like questions. If one is worried about earning trivial rep, one call always add an answer and mark it CW.
So, in case someone adds an answer in comments, what should one do (while not hurting any feelings perhaps)? (Ignore is not an option :-))
I wanted to open this, so we could direct any future comment-answerers to what the community opinion is regarding this (if any).
Note: I am not suggesting we have a policy/faq entry. This question would serve that purpose, if possible.