Will you (the community) be setting your username to your public username (a username you use everywhere) or something that's different from your public username?
Idk why, but signal feels more... personal(?) and I'd hate for general people to stumble across my signal account just by guessing whether my signal username is my public username.
I'd be fine if they got my Discord account, mastodon account, Lemmy account (they're all different usernames anyway) because they're public-ish accounts. Signal feels less public and I'd want to go with a username that only I can send to people I know.
It looks like there will be a message requests area and it looks like usernames can also be changed (should a username ever be doxxed).