Yeah, it’s definitely a weird problem. My initial reaction was something along the lines of “Isn’t there a decentralized way to do this?!” and…to my knowledge, there really isn’t? Like, you could distribute knowledge of user account associations across every instance in a peer-to-peer way, I guess, but that’s kind of ridiculous and pretty wasteful.
I think having small central services that improve the quality of life for decentralized services is largely a good thing, so long as they’re open source and not just some corporate product with vendor lock-in. It does kind of feel like a contradiction in terms, sometimes.