Actually, I don't think this is right. The creator of a group or "shared to group Y" chat/posts can generate a shared key for use within that limited friend gro

Actually, I don't think this is right. The creator of a group or "shared to group Y" chat/posts can generate a shared key for use within that limited friend group. Their individual posts would be encrypted validated by their own private key, but all posts among the group would also be encrypted against the group chat. Struggle here would be that anyone who gets the shared key would have access to view and potentially add to the group.