Beehaw defederated from other instances as users were getting around bans by creating new accounts on those instances. The admins in question are talking about how to address this.
Lemmy isn’t really set up for that. Its current structure is such doesn’t allow for that, and developers are still trying to do more for new user verification.
This is something that larger websites spend a ton of money and developer time to fight, which is something Lemmy currently doesn’t have.