I’m not positive this is a winner for normie users. The exclusivity of a user name is important, I want @mark, not @mark.abcdef while I know there is an @mark.abcdęf out there.
It might not be a thing for “normie” users, but the tech-overlapping crowd has been all about domain name based handles for quite a bit, and many are registering domains specifically because of it. This isn’t something they’re doing on a whim, they’re doing it in direct response to demand.
Two @ symbols? I think you're thinking of how Mastodon works. Bluesky doesn't work that way. Your username is the domain itself, not @username@domain. If you own the domain brian.pizza, your username can be @brian.pizza. If many users will share a domain, they are simply given a subdomain -- @brian.someserver.lol, etc.
But you see, there is no @mark. There is @mark.bsky.social (on the app instance that we currently call Blue Sky) but when federation happens and people start running their own instances, those users will be namespaced on a different domain (@mark.marksinstance.io, @mark.someinterest.club, etc.) Right now snagging a coveted handle early still feels nice like you would expect, but its uniqueness and the ability to use the name sans-domain when referencing will be gone if/when decentralization happens.
Well, only one person is going to get @mark, so this certainly isn't any worse for normal users than "every service forces you to get a bespoke username" as in practice you end up being mark_h.23 or something ridiculous like that.
The thing is, there is no @mark, if you have @mark on bluesky, your username is actually @mark.bsky.social. Every user is attached to a domain name no matter what, so this feature lets you at least use your own instead of theirs.
