Small nitpick, the domain name used for a ATProto identity is decoupled from the server that hosts that users data. A username is established on ATProto by creating a TXT record of the users DID (essentially a public key). This is not identical to ActivityPub, because the users data is hosted / managed by the server that the A/AAAA record points to. ATProto users can migrate their data from server to server while maintaining the same username. ActivityPub users cannot.

Also, Bluesky is a centralized view of the data in the decentralized ATProto network. This means you will never end up having the problem where searching for a user on one instance will not show up because they are on another instance that they have not federated with. There are obviously tradeoffs with this, but IMO they do seem sensible. The nice thing about Bluesky is not that it is decentralized (it's not), it's that the data that it let's users interface with is decentralized, and if something goes south with Bluesky, another application can be built on the same data and users can migrate without starting from square one.

This solves only half of the problem (migration). It doesn't solve the problem of different people signing up on different servers using the same handle. Is there anything stopping me from making a stephenking account on another server?

My "nitpick" was on the use of the word "server". The domain name used for a username is decoupled from the server. But no, there is nothing stopping you from making a stephenking subdomain on another domain. Just like there is nothing stopping you from making a website at google.mycoolwebsite.xyz.

But there are moderation lists that you as a user can subscribe to. It wouldn't be hard to find a moderation list for impersonators, which would solve this problem for you.

You've highlighted the exact reason this is a problem for mastodon and not for bluesky: on the latter, there's a default, so people who don't realise why it matters don't need to worry about it.

For the record, there are other differences - on Bluesky, you use your non-default domain to login in exactly the same place, there aren't 'weird gaps' between different domains.

It’s already exactly the same problem.

@zuck.bsky.app

and

@zuck.meta.com

are two different accounts.

The only “problem” bsky solves is choosing a server. But if ATProto becomes widely used, the problem will appear as in Mastodon today. The only way to avoid it is for bsky to never become really decentralised. So yet another VC-backed social media company.

I think this is why this is in truth, an aesthetic choice masquerading as a conversation about technical implementation.

I think there's no two ways around it, @stephenking.bsky.social looks better than @stephenking@mastodon.social.

Blue Sky does the names better and opts people into a default server at the moment, and I would say their desktop and mobile experience is a bit better, and that feels like they've solved something specific and technical even though, as you pointed out, the issue with domains is the same in each case.