If a server were an obvious conduit for disinfo then other servers could defederate from it. But if it was different accounts on different servers mixed in with authentic users then it's almost impossible to remove. What tools does mastodon / lemmy even provide to spot inauthentic behaviour? And because we're talking different servers run in different ways there is no clear picture from above that can be formed in the same way that a centralized social media platform might have - identifying suspicious clusters of nodes or traffic.

As for federation's future we'll wait and see. Both bluesky and threads are talking of providing federation protocols - threads using activitypub and bluesky it's own API. As for Mastodon & Lemmy I see a lot of positive interest in these things. The fact we're commenting on Lemmy instead of Reddit says a lot.