Microblogging with ActivityPub

Microblogging with ActivityPub

This is absolutely correct.

However, one way to somewhat mitigate your specific attack scenario is to refrain from sharing posts from newly-seen servers for a week or two (but allow admins to sample them.) This could make the attack too expensive and the bad actors more likely to be shut down before they can spread garbage to the general public.

There's also a trust issue. You have to trust the admins of your ActivityPub server to do their due diligence before accepting content from random instances. (I assume they can control this? Not 100% sure.)

So far, at least, Mastodon is way better than Twitter when it comes to civility. But now that George Takei is on, we'll see how well it scales. 🙂