We have discussed what our policy should be towards answers without references here and here, and have discussed answers in comments here. There seems to be a general consensus that answers of any kind without support, whether in answers or comments, should be discouraged if not deleted.
However, as sites in beta have a tendency to fluctuating expectations due to (among other things) adding new users and losing others, I think this issue needs revisiting.
I know that there are some users who strongly disagree with any deletions, even of bad - and even harmful - answers. We do have poor quality answers with down votes which have been left as examples of what does not meet this site's standards for new users. Personally, I favor this because users might not make the same mistakes over and over again if they have examples of low-quality answers. But that is probably best addressed in a different post. My question refers specifically to comments.
A user recently made this observation:
Answers in comments are officially frowned upon in every exchange I follow, but actually quite common and tolerated in all of them. ...I think you'll be battling them daily if you take a hard line on it.
I agree; this has been my experience as well on every site I participate in. Some are very accepting of it - and condone it in meta - even though in theory such comments should be deleted. One option a user has is to flag such a comment for a moderator to evaluate, and this is then handled differently on every site. Another is to invite the commenter to post an answer, which is sometimes accepted or declined graciously, but other times met with great offense (e.g. "this is good enough because it's correct. I don't need references to tell me I'm right.")
My feeling is that there is no way to judge a a good or a poor answer in comments since one cannot down vote them or check the references, therefor they should be deleted. I also know from experience that many people post bad answers in comments (on every site), and a challenge to those "answers" often results in an unpleasant and disruptive comment war. An immediate deletion with explanation can reduce the number of comment wars over this issue.
My question is, should all answers in comments be deleted immediately?