@davew What I'm getting at is, as I understand rssCloud (like I said, very cursory research just earlier), when someone follows you you get an IP address or a hostname. Which can be a server somewhere (potentially giving multiple people access to the feed) or the person's home or their VPN or whatever.
With ActivityPub, when someone follows you, you get their account. Which of course doesn't need to correspond to an established identity, but it still seems like a qualitative difference.