"Answer in comments": A comment which is a very short attempt to answer the question or solve the problem.
Answers in comments are a very common phenomenon on this site. Some questions have one while others have three and still others have 7 answers in comments (and 4 more deleted). This is not what comments are really designed for.
According to the help center:
Comments are temporary "Post-It" notes left on a question or answer. They can be up-voted (but not down-voted) and flagged, but do not generate reputation. There's no revision history, and when they are deleted they're gone for good.
It also states:
Comments are not recommended for ... Answering a question or providing an alternate solution to an existing answer; instead, post an actual answer (or edit to expand an existing one);
The largest issue with answers in the comments is that they are not subject to the usual quality controls which are applied to answers. They can only be upvoted and flagged, not edited, commented on, downvoted, and everything else.
On the other hand, often users will not migrate their comments to propper answers even when asked, so by deleting the comment some value is lost.
What should we do with answers in the comments on this site?