> I agree with all of your points except for anonymity.
I think the result is well-identified but not the cause:
> This creates extremely unproductive conversations without consequences. Platforms such as Twitter propel this behavior to new heights. When it was local, you'd lose friends for being unpleasant, you'd lose credibility in your community for being inflammatory.
In real life, if you accidentally invite a local Karen to your party, they show up and screech at everyone and don't get invited again. Karen is thereafter stuck at home alone screeching at her cats. Problem solved.
On the internet, the local Karen screeches and other Karens from all over the world retweet it. Karen is thereby emboldened by the attention and joins a roving band of Karens who blanket the world in screeching and hatred like a plague of angry locusts. Which can happen even if Karen is her real name.
What prevents this in real life isn't the lack of anonymity/pseudonymity, it's the lack of equally deranged local compatriots providing a support network and validation for ridiculous anti-social behavior.
Presumably what's needed is more localized communities. It shouldn't be Twitter and Facebook but rather separate communities based on interests or locality and moderated by people who are themselves members of the community being moderated rather than some unaccountable corporate monopolist.