@mro The actor ID should be the thing uniquely identifying an account, yes. However, in conversations we use tags/handles and not AP IDs, so we gotta construct these handles somehow. Your approach, using the AP host, is equally as idiosyncratic as using the WebFinger host. Both ways exist in the wild – Pixelfed, Misskey and Friendica do it the way you do; Mastodon, GoToSocial and Iceshrimp do it the way I do. I just prefer this way because it lets people use their domains more easily. 🙂