From this point of view I would almost prefer sites to adopt just overall stricter rules, strictly moderating both tone and "off-topic" content tuned to each individual forum.

I think that a lot of communities had a passion for cultivating a freedom of expression, but actually had a lot of unspoken/unrealized rules in mind.

In my opinion a lot of communities would gain a lot by a flashing banner "We decide what content we want on our platform and we will take arbitrary action to protect our choices". In practice is what social media companies are doing now even if they cannot state it as such (in part for legal reasons and in part for marketing reasons)