Asklemmy

Since you’re the instance hoster you have the right to

Not sure that's a helpful factoid. He does indeed have that right (in most countries). But he also has a right to use a cheese grater on his dick. It's just "not recommended".

The system is federated, and those who don’t agree by the rules can post on another instance if they don’t like it.

Email itself is federated, and is the canonical example of federation. I believe that the Mastodon and Fediverse itself uses it as the goto example when explaining themselves to journalists.

But email isn't an open system where anyone can connect anymore. Only gigantic companies are allowed to participate on a meaningful level. Anyone else who attempts to do so finds it impossible, and if they complain about it, they are met with derisive rebuttals about how only spammers would want to do that anyway. "Just get gmail!"

The fediverse needs to figure out how to deal with that particular endgame, but it won't even be obvious that it's a problem until it is already impossible to do something about it.