I'm a participant on a political discussion forum that enforces strong civility norms (eg anti-snark), and it very much works. It's very popular these days to say that civility norms are a Trojan horse for enforcing conformity. But the breadth of viewpoints I've seen expressed there is 10x as high as anywhere else, and conversations are consistently polite, insightful, and intellectually honest. It turns out that filtering out stupidity and emotional incontinence leads to adult conversation.

More importantly, the norms make any given person feel safe acting like an adult, even if they'd otherwise be inclined not to. This is a big problem with much Internet discourse: putting thought and nuance into a comment and taking your interlocutor seriously is easily deflated with mockery and disdain for "tryhards" or "effortposting". The natural equilibrium is obviously going to be that even people inclined towards intellectual honesty end up in the mud flinging shit at others. Consistent, high-quality moderation around civility prevents the temperature from rising and allows you to actually learn something from every exchange. (It doesn't hurt that the filter effect of these norms mean that the average commenter ends up pretty intelligent: even when someone is wrong, I tend to learn something)

Tldr: the norms you're describing work very well IME