Privacy

This is real false dilemma that people often raise. There's so many tools that Signal can use to stop spam. Do you get spam email? Almost never - even on E2E email, because reputation blacklisting solved it. Signal already only lets accounts message other users in their local contacts list or added by username.

Examples off the top of my head: If a new account is registered it can have a 'gradual release of abilities' whereby it can only send 3 messages first day, 10 first week, etc. Same for adding users by username. Signal already has spam-account reporting capabilities that block accounts after too many reports. Simple. Solved. And the payoff is that everyone gets complete privacy of who they are during signup.

BTW I already get spam on Signal. Here's the latest from just 2 days ago, know nobody by this name and don't recognize her, standard pretty god-botherer bait profile, user photo looks like AI (light reflection left eye very different to right eye):