I moderate Skeptics, where we have two specific issues that probably are not so bad elsewhere but are terrible for us:
- We only allow evidence-based answers
- We allow very controversial questions on inflammatory topics (e.g. school shootings)
The problem is that people avoid the "evidence" rule by abusing comments to write "pseudo-answers"--usually, in fact, their personal opinions, without any evidence to back that up. Of course this often leads to flame wars, with people literally insulting each other, and often even purging all the comments does not prevent the flame from restarting soon later.
So we do moderate the comments by asking people to calm down. We do moderate the comment threads by nuking them all when things are out of control. Yet, in some cases we have to go through 2-3-4 cycles of "purge all comments".
It would be useful to have the power to prevent commenting on a post altogether for a limited time. A simple "lock" would penalize the OP without any reason. We can certainly do without this feature, but this would be a real time saver. Furthermore, I do think it's better to prevent commenting if the alternative is having 100s of deleted comments, at the very least out of respect for our users' time.