The discussion[1] about replies as an abuse vector is so funny.
A bunch of techies trying to find a technical solution to a social problem.
Guys, IT DOESN'T WORK to ban replies or change replies or ban quote posts or "do it right this time" or whatever.
When there's humans, there's abuse.
The only way to deal with it is moderation; that is ban or block instances and users that are abusive.
[1] https://toot.thoughtworks.com/@mfowler/110841059611104925