I never think to turn to flagging - and end up engaging, and it is usually fruitless.
My worst experiences in these forums have been with people who may have disagreed with my comments, or simply not like them, projecting meaning on to my statements that was not intended and in my opinion not there. I clarify, receive more projections, rinse repeat.
Such situations are difficult to flag as a matter of mis-behaviour may be shades of opinion. My gripe is once I have clarified, and the mis-representations persist, in that case we have strayed into poor behavior, as in a form of mild trolling, that should be moderated. Yet these situations rarely stand out as flags.