There are certain metrics that can be used, such as the ratio of upvotes to comments. I red it somewhere that a post with 100+ upvotes but no comments can be spotted programatically.
HN I see sometimes where it isn't the link that's the goal, it's the top comment for the link. So the OP is a bot with a clean record but the top commenter is the narrative pusher.
Plus there's the good old link to the blacklisted but unbanned topics. Check out J**n P***n's spam and they aren't blocked but the accounts that post them get a strike.
It's a moving target and they get better all the time. I red it somewhere that you could post about i*l and p***e and in minutes the bots would appear, but the i word has gotten a lot more sophisticated lately. Their s emm emm operation is among the best in the world.
Lastly, many state actors are very good on offense (S and the I word) but everyone is terrible on defense. It's still the wild west out there and the bad guys are winning.
My $0.02 YMMV