When you cross paths with a troll or otherwise troublesome user on an SE site, is it okay to submit a mod flag that says something like "hey, check out user X in the comments, I think he might deserve a ban/mod intervention"? Or would that be considered an abuse of the flagging system?
Moderators are in charge of assigning suspensions. Flagging for moderator attention is the most direct method of communicating to the moderators.
That said, a lot of suspensions accrue due to a high amount of flagged content. I suggest that if you must flag a user for this kind of reason, flag it because of the bad behavior and not to suggest a suspension. Leave it to the staff to conceive whether suspension is even a reasonable resort or not.