Occasionally when I see a big long thread of obsolete-chatty-argument comments, I'll just flag one of them, select "other..." as the reason, and just request that the whole thread be deleted (rather than creating a dozen flags).
Maybe I'm doing it wrong and should just make all the flags (should I?), but here's another case in which an "obsolete" flag was rejected (as an example of this being useful on things other than long chains). Perhaps a brief clarification could have helped.
I envisage something like this, where the text area can be empty if it's anything other than "other...".