ATProto

Roughly 99.9% of ATProto accounts sit on Bluesky's own servers and never register a backup rotation key. That single gap turns the operator into a custodian who can impersonate you across Tangled, Grain, and Leaflet, not just one app.

The theory said you would hold the private keys. The product decided otherwise, because making millions of people manage cryptographic material would have crushed signups.

The fix is unglamorous: make backup-key enrollment mandatory at account creation, baked into the client.

His argument is architectural. Mastodon bundles hosting and app into one server, so federation is server-to-server and identity is tied to your home instance. ATProto splits them: your data lives in a Personal Data Server, while apps aggregate across everything, like Feedly over the whole blogosphere.

Engineers in the thread pushed back hard. There's one PLC directory, a handful of relays, and in practice one AppView, all mirroring Bluesky's moderation. Decentralized in protocol, one company in practice.