ActivityPub addressing is really somewhat complex and pretty much any server is going to abstract it with things like at-mentions, sometimes making different assumptions. When I reply to lemmy posts from my microblog.pub server, I sometimes need to make sure to include both the user (@elena@lemmy.world) and community (@fediverse@lemmy.world) if they happen to be on different domains. Otherwise my server's addressing won't send it to the right place. And I doubt other lemmy instances will see this post unless I tag them too.
@ChasingEnigma@lemmy.world DeviantArt - I like separation between art, literature, and regular status updates, and the ability to group posts in your inbox into folders by who posted them. Or, more realistically, any of the various furry sites that work on a similar model and have less potential for cultural conflict.