@simsa01 If both authors are subscribed to, both authors' notices will be shown. If they are just "known", that doesn't mean anything and there is no subscription link setup and no reason why I'd want to host a bunch of crap this "known" author writes which I have expressed no interest in (and am not a direct recipient of).
The "remote retrieval" (i.e. fetching a missing "parent notice" retroactively) or making a conversation-subscription is how this should be solved. The latter also means one could _unsubscribe_ from a conversation (which would be impossible if nodes just gladly accepted unrelated notices).