The S2S spec says:
Upon receipt of an
Addactivity into the inbox, the server SHOULD add the
objectto the collection specified in the
targetis not owned by the receiving server, and thus they can’t update it.
objectis not allowed to be added to the
targetcollection for some other reason, at the receiver’s discretion.
OK, this is straightforward.
But what are the semantics of that: The vocabulary states:
Indicates that the
actorhas added the
So, the actor in control here is at the sending server, and they want to add something to a collection (the
target). The ActivityPub now says that they can do that for collections under the control of the receiving server, so an actor on server A controls addition of an object to a collection owned by server B here.
To me, that makes no sense – server A should only inform me of additions of objects to collections owned by server A itself., or not?
Of course, that qualifies as “not allowed for some other reason”, but I still wonder what the intention of the spec with the first bullet point is.