On the other hand, Discord used to allow arbitrary usernames and would add a suffix for when you needed to disambiguate (e.g. if you used the username JohnDoe, your "id" would be something like JohnDoe#12345) but over the past year or so forced everyone to pick a fully unique username. In this case, the decision seemed to potentially be financially motivated, given that people with subscriptions were given priority for claiming usernames, and historically there really hasn't been much reason to pay for it in the first place.