I’m not sure there’s a good automatic threshold for throttling a topic. Usually, it’s best deployed when a user is “on tilt” or posting inflammatory posts at a high rate. It can bring the temperature down on a topic and get multiple voices involved while keeping the thread from going off the rails and turning people off.
I wouldn’t want to trigger it automatically off of just the frequency of one or two users posting, but maybe in combination with community flags, that could be a good criterion. I can’t think of an example where it has been used to good effect that hasn’t involved both factors - frequency and flags.
ETA: I could see it being a useful intermediate step between nothing and shutting down the topic.
