Lemmy doesnt do any such verification, because we already trust the community by following it. Even with authentication, a malicious community could do numerous bad things like banning innocent users or not announcing certain activities. So authentication would only solve part of the problem. And in practice, users would notice such manipulation themselves and migrate elsewhere.
This is quite different from the microblogging world, where any user can make a controversial post which gets shared across the whole network. So verification is more important there.