My only thought is "scale only through federation". It's impossible to moderate the content of a billion users. It's pretty easy to moderate the content of 1000 users. And if you're moderating the content of 1000 users who mostly come from an actual community (physical or subcultural) that shares the same values, you don't have to have your moderation rules enforced worldwide to the lowest common factor of different value systems, or by outsourced wage slaves from a different culture without any context.
Source: I'm a moderator on a Mastodon instance with about 1000 users (connected to the larger Fediverse of about 2 million users). We've got 5 moderators, and we respond to reports (either by or about our users) promptly and well. We don't have to police the behavior of the whole Fediverse (just our users), and we don't have to protect the whole Fediverse (just our users).
Source: I'm a moderator on a Mastodon instance with about 1000 users (connected to the larger Fediverse of about 2 million users). We've got 5 moderators, and we respond to reports (either by or about our users) promptly and well. We don't have to police the behavior of the whole Fediverse (just our users), and we don't have to protect the whole Fediverse (just our users).