Devil's advocate but what if someone registers whoisearth on another instance and starts spewing vitreol? I'm sure many people would be concerned about any online reputation they've built then get cut down simply because someone wants to be an asshole. How would that scenario play out? Genuinely curious.
And what if someone registers whoisearth on Gmail, Outlook, Facebook, Instagram, Twitter, LinkedIn or PornHub? Have you registered your name on literally every social media ever existed? This isn't a new problem, or one that is created by the concept of federation.
Federated services are like email. Just like your email address isn’t just “whoisearth” it needs the @gmail.com at the end to be the exact one to reach you, same as in Lemmy, it’s your name plus your instance that matters.