As a board it is slightly less easy to troll than other boards, due to the need to have been posting for a certain amount of time. AIBU you can join and post the same day.
Of course, posters should be aware of what they say but often the advice tends to be practical rather than salacious.
If you think it's a troll, why engage? Anything you post simply bumps the thread and means it might end up in active, as the fisting thread did. But sometimes it will be a real thread, and then all that is achieved is embarrassing or, worse, slut-shaming an OP that asked a genuine question.
It would be exactly the same as seeing a post in AIBU that you think is trolling, but does always sound the chance of being real, and then what does a sarky comment achieve then? It's the online equivalent of "if you can't say something nice, don't say anything at all." MN has a great funny vibe sometimes, but there's no need to pile in.
And if it is real, and the OP gives off neither red flags nor a sense of looking for salacious details, then what is achieved by saying "christ, no, that's disgusting." Would you go on a recipe thread asking for lamb dinners and start ranting that you hate eating lamb? Would you go on a camping advice thread and start ranting that you hate camping?