It might be the case that the designers of email and the designers of ATProto and the designers of AP all assumed the owner never changes. But I think the actual behavior of the protocols in the event of a change is different.

For email, if the owner changes, the new owner gets full control. This is nice for the new owner, but maybe not so for the old owner, because now any emails meant for the old owner can be read by the new owner.

For ATProto and AP, it sounds like in the event of an owner change, things kind of break. This protects the security of the old owner to some degree, but means the new owner can't really do much.

Email is more like physical mail - you send something to an address and whoever lives at that address gets the mail.

The described ATProto/ActivityPub behavior would be like trying keep the address tied to whoever lived there first.

Persistent identities are a nice goal but treating transient identities as persistent is not. A better designed system would use the domain name system only to look up the current identity associated with a name instead of trying to permanently tie the name to an identity.

No, since email is delivered to whoever owns the domain at the time the email is delivered. Besides a spam reputation score — which is a problem — one mail server doesn't retain a long-term trust relationship with any other.

Not really? Email is a dinosaur of a protocol that doesn't properly handle authentication to begin with.

Anyway other protocols or implementations making the same class of error doesn't change the fact that it's an error and that it causes real world problems for users such as described in the linked page.