they did that already. you can sign up with just an account name now, i ditched my phone number from my account after it rolled out around a month ago.
Serious question: what should they, or some idealized privacy-first messaging service, use for as a account-id + authentication? I will need some reasonably cost-effective defense against mass abuse.
They could offer usernames tied to a one-time minimum donation, for example, let existing users vouch for new ones etc.
Yes, all more difficult than using phone numbers and outsourcing the proof-of-humanity problem to telcos all over the world, but in my opinion it would be worth it.
