This restriction has a few exceptions: it doesn't apply
on Meta sites
when both questions are asked by the same user
for ♦ moderators
Therefore, using a custom moderator flag is a good option. Please specify clearly why you're using a moderator flag instead of a regular vote to close; standard flags are always preferred and you risk getting a ...
Comment flags can only be acted upon (resulting in the deletion of the comment) or declined, there is no option to provide feedback (which is actually optional also for flags on post).
I didn't handle the flags on these comments, but I would have declined them as well. The comments show good community actions on helping a new user to understand the site ...
Thank you for raising this question. I see many people not understanding the not an answer flag. You are not alone to be confused here. Have you read through this post and the answers?
Why was my flag for "not an answer" declined?
What parts of the answer on why we decline not an answer flags in general might apply to the post you identified?
It seems flags can not re-flagged, given this check
You have already raised this type of flag and can no longer reraise it
So users who accidentally "dismiss" flags should be deleting the comments when flagging was legitimate.