There was a thread on lemmy.ml with somebody suggesting an invite system. One of the devs replied they didn't have the bandwidth to do it but invited others to look at implementing it, not sure if anybody's working on.
It's a good point that the current binary choice of federating vs. not federating isn't flexible enough. Mastodon has a couple of in-between options, not sure if they're the right ones, but at least points to some possibilities.
I don't think this place is inherently any more bot-resistant than reddit, it's just that bots haven't started to target it yet.
Great post. Can I quote a bit of it and add a link in my post on what Kbin, Lemmy, and the fediverse can learn from the experiences with Mastodon? https://privacy.thenexus.today/kbin-lemmy-fediverse-learnings-from-mastodon/