Ask HN: Is there any mobile messaging app that requires no phone number?

[aimhb]

I've found plenty of mobile messaging apps (LINE, Viber, WhatsApp) but they all require a phone number. Are there any that just have a username?

[gtk40]

Google Messenger? (Although Google accounts try really hard to get your phone number, I don't know that it's ever required).

Anything XMPP based.. you could just use any old XMPP server and client.