Something I'd like to see Lemmy and others adopt is a federated identity/reputation system.

My identity as @Zak@lemmy.world has only modest reputational value. It's moderately risky to let me participate in a new community, and busy moderators probably shouldn't give me much slack before banning me if I post something that makes me look like an asshole or a spammer. In a place with a high enough volume or vulnerable enough population, perhaps this account shouldn't be allowed to participate at all[0]. Someone willing to put a bit of effort into abusive behavior could create many accounts that look like mine.

If, on the other hand, I can prove that I'm also https://news.ycombinator.com/user?id=Zak, that's a more valuable identity. There aren't all that many 16 year old accounts on news.ycombinator.com. If I can also produce a verifiable token with some machine-readable facts about that account, such as its age, post count, reputation score, how many of its posts have been moderated, if it has ever been banned, etc... then communities could have automated criteria for joining.

Of course, communities would need to maintain lists of who they trust as reputation providers, which could also be shared to reduce the workload.

[0] Lemmy does not currently have tools to restrict participation other than only allowing moderators to post. I think it's going to need them.