> If the XMPP/Matrix people wanted to they could set up a trusted third party server to link identities to phone numbers just like Signal does Signal is even

> If the XMPP/Matrix people wanted to they could set up a trusted third party server to link identities to phone numbers just like Signal does Signal is even simpler: they use the phone number as the identifier. So you could have an XMPP server with a given domain, and your phone number as your login. The whole SMS dance for making sure you own the number. That already exists: https://quicksy.im/ https://quicksy.im/. And yet it doesn't seem to have attracted that many people. I don't think it was an issue of usability though, it is not so far from Signal, but a publicity one.