It's wild to me that
1. There are tons of replies in this thread. People have very strong feelings about signal.
2. Some people feel VERY STRONGLY that the pin numbers are stupid, and it has a terrible UX.
3. Some people feel VERY STRONGLY that the phone numbers are the simplest, most straightforward thing to use, and they would hate Signal if they didn't support it.
4. Some people feel VERY STRONGLY that they don't want their phone number used as an identifier, and it's a failure of Signal that they use them.
And it seems like many of these replies assume that their own position is the only possible one to take (or at least the only intelligent one!).
Imagine working on Signal and trying to create a product that pleases all these people, as well as even less technically minded folks, while having none of the usual analytics at your disposal to measure actual user interaction!
My hat's off to Signal. I admire their work but I don't envy their position.