What is the policy for answers written as comments?

Question

Different stacks seem to handle this to different degrees.

I recently flagged a comment made under a question which was clearly meant to be an answer; after three existing answers had already been submitted.
I also commented under this comment to the effect that the comment space should not be used for answers.

My flag was declined and my comment deleted.
Since then, yet another comment has appeared, which also should be an answer.

This makes it seem as though answers in comments, completely bypassing the voting structure, are perfectly acceptable.
Is there consensus for this stance?

My own personal stance on this is far better reflected by the policy on Photography SE Meta - Please put your answers in the answers section, even if they're short

Of course, we're all tempted to drop in short comments when a full answer might seem too much effort, but when the points raised are already in the existing answers, this seems a more deliberate bypass of the voting structure.

Answer 1

My personal stance is that I step in when a clear line has been crossed. In the case of someone providing a 2 sentence comment on a question, it wouldn't stand as an answer on it it's own and mods we be asked to delete the low quality answer. This is very much a relatively gray area, other mods may come down differently on issues like this. In general we try to make the site a welcoming place, and aggressive removal of comments in gray areas can be seen as unwelcoming by visitors, so when in doubt I'll often leave a comment up.

Where I often clean these comments up are where a comment thread turns into an answer after some back and forth with the OP, an answer has been posted by the commenter, and any important details from those comments have been included in the question or answer.

Regarding the reason to delete your comment, it was a meta comment about another comment, and not relevant to the question, so I cleaned it up. Same as I had cleaned up another heated comment thread moments earlier about disliking US wiring standards to a question about whether their wiring was safe. We tend to have a clear line when the comments are not addressing the Q&A they are attached to, and that's easier for me to make a decision on.