It's interesting that the same technology can be used for both anonymous reputation, and rate-limiting, in a decentralised way. I think that a lot of online services would be simpler to implement (and simpler to federate) if they could assume that:
* each account belongs to a unique human
* the account has an accurate reputation assigned to it by other humans
* there are reasonable limits on the amount of resources that each human can drain.
For example, imagine an extension to the Fediverse which implements something like a dating app, where you can register an account on any instance, and search for users across other instances, but those instances could enforce that you haven't sent out a million copy-pasted messages to everyone who vaguely matches your preferences.
I think that the "proof of (unique) personhood" guarantee is still the hardest part, although the Ethereum website does list a few active approaches to solving decentralised identity.[0] I'm also interested in the UniRep Social project, which was linked[1] from Vitalik's post, since that's the most advanced decentralised reputation system I've seen implemented so far.
[0] https://ethereum.org/en/decentralized-identity/#use-decentra...
[1] https://unirep.gitbook.io/unirep-social/
