PS the whole "a group of things [can't] share an internal world" spiel is weird and just plain wrong IMO. Humans could perfectly well share an internal world if the technical means were there.
I think you are dismissing this too quickly. Our internal world is part of us in a way a shared internal world would probably not be. A shared internal world would in certain respects not be too different from the external world, or a chat group, or a multi-player game, a space where several people interact. I have never thought about this, but it seems quite reasonable that the exclusivity of our internal worlds is a key feature. Why would I consider a shared space as integral part of my self?