"But under the hood, the #ActivityPub protocol doesn’t use full mentions at all. Instead, it uses actor IDs."
The actor ID for my main account is https://mastodon.social/users/crepels. In my case, there is a direct translation between the full mention and the actor ID, but that doesn’t have to be the case."
@crepels, 2023
https://seb.jambor.dev/posts/understanding-activitypub/
Intriguing. So in theory, the Actor ID for a fediverse account could also be represented in an app as @username@email.service or @username@xmpp.service 🤔