That's weird that you have to download from a whole other instance, I would have thought the client requests what it needs when it needs it, and points to some sort of UUID to another instance that can be queried later by a client.

I'm really lovestruck by the capabilities of ActivityPub and I want to work on a federated Tumblr alternative, but I just have not found the time with all the personal stuff I have going on currently, but ideally you wouldn't store everything on your instance (unless you rather cache it, now THAT makes perfect sense to me) you would let a browser request certain things via AJAX and maybe your instance could tell the other instance, hey guy you keep asking me for this waaay too often, can you cache it for me? kthxbai and those who don't do it would be considered broken instances and possibly rejected? Not sure I feel like the protocol is still way too young. Also not sure about the security implications but let's assume that sane SSL cryptomagic is a requirement for blogging instances (or just all of them).