Why was this flag declined by a moderator?

Question

This non-answer (previously accessible via https://superuser.com/a/1853110/380110) is obviously a comment on another answer, and not an actual answer. I flagged it as such while helping our community in the review queues, yet a moderator declined my flag. Why?

Answer 1

Well on review - I think converting to a comment would have been the appropriate thing. Mistakes were made, and I've done the necessary.

I can't undo the flag rejection so I hope this would be sufficient.