There is no username in ACME besides the account URI, so the UUID you’re suggesting isn’t needed. The account uri themselves just have a number (db primary key).
If you’re worried about correlating between domains, then yes just make multiple accounts.
There is an email field in ACME account registration but we don’t persist that since we dropped sending expiry emails.
2. Its consistent across an account, making it easier to set up new domains without needing to make any API calls
3. It doesn’t pin a users key, so they can rotate it without needing to update DNS records - which this method assumes is nontrivial, otherwise you’d use the classic DNS validation method
If you’re worried about correlating between domains, then yes just make multiple accounts.
There is an email field in ACME account registration but we don’t persist that since we dropped sending expiry emails.