Going through the list of recently migrated questions (10k), some of these really need some editing or other moderation.

What you see quite often on those questions are comments like:

• not seeing how this is a ServerFault question. – ceejayoz 1 hour ago
• Which forum should I move this to? StackOverflow? – Mark Lutton 1 hour ago
• It has even less to do with StackOverflow. – ceejayoz 41 mins ago

Now that the question is migrated, they don't serve any purpose and distract from the actual problem.

Should I flag for moderator attention to have those deleted?

If so, how should I do it?

• A comment flag, specifying the "Other…" option, asking for comment cleanup?
• A normal flag on the question itself, with the same reason as above?
• A flag on each individual comment using the "Obsolete" flag reason?