When I am flagging answers I read
This was posted as an answer, but it does not answer the question. It should possibly be an edit, a comment, another question, or deleted altogether.
This is very broad and does not say when an answer is eligible to (or should) be flagged.
Usually, this leads to rejection reasons that do not match the description or flag reason:
(^ wrong rejection reason, complete opposite of what I said)
(^ wrong rejection reason, OP has explicitly excluded the answer)
(^ wrong rejection reason, OP has already tried)
And so on...
There seems quite a mismatch in what (high reputation) users and moderators believe is wrong, or at least I can find no general text that tells me what to belief. I also don't like the guessing and debating that results from this, whereas understanding the moderator's view upon this can help a thousand times.
Hence, my three questions to the Super User moderators:
So, to get this cleared up, in which cases should we flag "not an answer" answers?
How should we flag eligible answers? What do we put as the close reason to be clear?
What do we do when the answer is ineligbile for flagging, but isn't a good answer?
Here is an unmodified TL;DR summary of the important bits of the ♦ answers:
If the post makes an effort to answer the question (even if it does a bad job of it) then it is an answer and this particular flag doesn't apply.
Just flag them as not an answer. If you feel they're an odd case then flag them as other stating "not an answer; because x y z" or something similar.
Add a comment explaining the problem (or upvote any comment that has already done so). If it's particularly bad for some reason then downvote the post.
We need to remember that moderators are human exception handlers.