> single very clear focus or purpose for the forum

It's the case on that forum and the off-topic discussions (religion & politics) are accesible only to accounts older than 1 year, so it helps to limit shitposting in those discussions. Accountability for your opinions in that case just mean getting mocked by other people (I said free speech, not nice speech).

I just wanted to show an counter-example disagreeing with your (apparently) absolute position.

> Accountability for your opinions in that case just mean getting mocked by other people

Yup! That's one of the good ways of holding people accountable.

Also they have tags that will appear above the user portrait, to indicate the more troublesome members. They are applied by the few moderators. They include shiposter, idiot, edgy...