I recently mod-flagged a comment under a question:
You haven't mentioned which version of Windows you are running. Have you got Sticky Keys enabled?
Importantly, the OP commented immediately saying "thanks, it was the Sticky Keys". In the flag explanation field, I explained that the comment should be converted to an answer, because, while it is phrased as a question, it is offering a solution that can very easily be edited--in answer form--to more of an 'answer' or suggestion, like:
You haven't mentioned which version of Windows you are running, but check to make sure you don't have Sticky Keys enabled"
This sounds more like an answer and yet doesn't change the intent or content of the message.
The flag was declined. This seems like a clear case where the answer was given in a comment and that answer solved OP's problem, and I feel this action is warranted to award the answerer due credit and to prevent a useful question with a useful answer from being eventually Roomba'd.
Could the declining moderator please explain why they declined the flag?