ATProto Spaces alpha adds non-public data to the protocol

Sources: atproto blog, HN discussion
Summary: The atproto blog published an alpha of Spaces, which adds non-public data to the protocol. Spaces give access control rather than confidentiality, and the data stays readable to anyone admitted to a space.
Why it matters: Settings, drafts, and gated communities become buildable on atproto, under a model that controls admission and not disclosure.