Riffing on your "single space" and "getting federation wrong" ... I think there's something to say about the lowest common denominator effect in a federation of multiple platforms where unless all/most platforms/users support something than it doesn't really exist as a feature on the fediverse.
Quote posts exist on some platforms, but not mastodon, so it doesn't matter if you're microblogging.
While I'm all for platform diversity, I feel like many don't realise this.