I don't know either but theymos seems to take a hands off approach for most things and let the community take care of itself. Things like the feedback, trust and merit systems all really police themselves and anything else just requires more manpower thrown at it and that's something theymos probably doesn't have the time or energy to do. Freedom is great in some aspects, but inaction in other cases just leads to abuse en masse and once people realise they can get away with something the problem just gets exponentially worse the longer you leave it.
Self-policing can work but I think the community is lacking some tools to do it properly. Merit seems to be a step in the right direction. I would like to have some visibility of how "report to moderator" works in the backend, e.g. which reported posts get deleted, which don't and why, etc. That would help to make post reporting more efficient. Even just seeing which posts have already been reported would save a lot of time.
Beyond that, asserting control over sig campaigns would require some sort of trust-like or merit-like structure where only approved campaign managers can do it and then can be held accountable by some metric. Otherwise they would just manage the campaigns outside of the forum. If theymos was willing to establish such structure the rest could probably be self-policed. Unapproved signatures could be reported. Shitposters carrying approved signatures could be easily reported to campaign managers and said managers could be penalized/removed if they fail to take action.