Very interesting!

I agree with your point that a user accou t without a canonical URL to send messages to could nor have an inbox, and therefore never get DMs or notifications if somebody commented on their post.

I had not thought of that before but it seems obvious to me in retrospect. Obviously, to receive messages, you need some kind of machine-address, where these messages will be sent to. And that’s what this is for:

They expect it to point to a valid JSON-LD document describing the actor which they can request.

Because it describes the inbox address.

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Your data hoster is the instance you have your account on, not the one the community is on. Your instance just shares the posts you make on it with the community, but all it receives is a copy. The canonical version is on your instance, discuss.tchncs.de.

That’s truly fascinating knowledge, thank you. It makes sense because in the ActivityPub protocol, each user has an outbox, and published posts go there. So of course, other communities simply reference that instead of actually holding the post.

This means, then, that communities aren’t actually so much lists of posts, but lists of references to posts, i.e. when i post to /c/a@lemmy.world, that community simply gets notified about the canonical link to my post, which actually resides in my outbox on this server. Thanks for making me think about all of this!