We specifically let all Readwise subscribers in at the same time (with an email that went out on the same day), giving them access before the general public. I wasn't aware there was actually more we could have done. Were we supposed to let people bid on them? How would we deal with conflicts across two subscribers?
But the best approach is not to launch a service with usernames - you gain NOTHING. In fact, you can only piss people off! You launch the service, you allow users to link other social identities and you then decide what to do.
On goodreads/X, we have a loooot of users who use neither of those, so I don't think that approach would have work.
I take your feedback and will try to do better next time. We really just didn't think people would care that much, as far as I can tell you're the only person who has brought this up with us.