I understand that it may be problematic sometimes but this was very smooth. I didn’t even say anything.
A: what’s your number for the whatsapp group Me: I don’t have whatsapp because of facebook. B: ok, we have to use signal then A: ok
And that was it. Life can be very easy sometimes
XMPP is way more open and interoperable than all the solutions available, it works like email any user can can talk to any other and doesn’t depend on a some proprietary / closed service centrally owned by anyone. That’s a good selling point.
XMPP doesn’t really force users to sign up with email address, it just happens that XMPP addresses use the same format, many public servers will give you an address like username@server.example.org that is never mapped to a real email address and only works for XMPP. The decision to actually ask people for their real addresses is up to who owns the server and won’t be directly exposed on the XMPP network.