So the reason Session never took off is probably because exchanging contact information is a big hassle, effectively barring users looking for convenience?

I don’t know that their security is “broken”. It may be, I don’t know. But also without anything that connects you to any particular message, it seems that – in itself – is a pretty good form of security.

I just don’t get why people accept Signal’s justification for requiring a phone number. They absolutely don’t need to (session proves that). It is certainly possible for them to say, “If you register without a phone number and access to your phone book then you will lose automatic discoverability by other users of Signal — meaning that you need to find another (physical) way to exchange your Signal username with your contacts”. They CAN do this. I think many users, like myself, would be fine with this tradeoff for greater anonymity. For some reason, they have steadfastly refused. The reasoning behind this refusal is what bothers me.