And, of course, blogging has this! There is a comment form at the bottom of this page - and I moderate it. If you post something stupid, I don't have to subject my audience to your inanities. I can (and do) block users from commenting.
ActivityPub doesn't have this (yet). It's much more like a public mailing list. I can block or mute you - which stops me from seeing your abuse - but doesn't stop anyone else from seeing it.
Should ActivityPub have something similar? Yeah, I reckon so. I'd like to be able to say "Anyone I know want to go to the pub tonight" and only have mutuals reply. I want to prune away spam or repetitive replies. It would be helpful to have a conversation in public that other people can't interrupt.
The UI would be complex. And the social model needs a bit of work. And there are some technical challenges around syndicating which replies should be included.
But, ultimately, social media should respond to the needs of its users.
