The recent ban was executed through administrative action. That's O(1), albeit apparently with a high constant factor if Kaj's posts are to be trusted. There's been a lot of drama surrounding it, but that doesn't have anything to do with scalability.

(Personally, I'd say most of the drama has to do with preexisting cultural and administrative issues that this has dragged squirming into the light, and takes the late unpleasantness as a proximate rather than an ultimate cause, but we may reasonably disagree on that point.)