ActivityPub can be private in the same way email is private. All the people in the recipients chain will have a copy of the object you're sending. If in these recipients there's the Public namespace, then yes, you can't talk about "private" any more, but outside of that ActivityPub supports private interactions.
As a followup on this discussion, I actually spent half a day today to add private messaging to my ActivityPub service. It actually works.
ActivityPub can be private in the same way email is private. All the people in the recipients chain will have a copy of the object you're sending. If in these recipients there's the Public namespace, then yes, you can't talk about "private" any more, but outside of that ActivityPub supports private interactions.
As a followup on this discussion, I actually spent half a day today to add private messaging to my ActivityPub service. It actually works.