Comments marked as "no longer needed", are to be deleted, if the flag is acceptable.
"Not constructive" => "Rude or abusive" or "No longer needed"?
... so regardless of which flag you use, it's essentially just a bat signal to mods that "this comment should be deleted"
In fact this particular flag is introduced for making deletion easier.
Comments are moved to chat when there are too many of them (bit noise), however they are still relevant to the Qn's present revision.
Usually, answers are retained even if the Qn changes revision. But comments are temporary & ought to be deleted, when they are no more relevant.
IMO, in your case, the original comments should have been deleted, but since they are not, the comment containing chat room link can be flagged as "no longer needed", should you don't want any traces of them.