I've seen some discussions here on meta-SO where moderators have said that the appropriate action for a user who appears to be trolling in comments is to click the "Flag this comment as offensive, spam, or hate speech" flag by the comment.
Maybe you could include "trolling" in the list of reasons to flag a comment? Until I read this on MSO last week, I didn't think trolling was a subset of "offensive, abusive, or hate speech." I guess you consider it part of "offensive", but to me offensive would be something like unnecessary profanity or vulgarity.
Or maybe the problem is just that my personal interpretation of "offensive" is more narrow than others'? I don't know, just a suggestion...
(Note: when I say "trolling" here, I mean someone who makes comments that seem to be designed to start and/or egg-on an argument, rather than lead to thoughtful discussion.)