Banning Mastodon users on Lemmy communities

Migrating changes the account completely. There's a connection between the two, if the person chooses to do it that way, but they don't federate as the same account.

So you'd have to ban the new account as well.

Are you trying to ban individual users for individual reasons? Or are you trying to ban all mastodon users?

I doubt it specifically because when joining a new instance you're making a new account.