[detaro]

I find usernames a lot easier to communicate than phone numbers, and they are cheaper to move to another phone provider. And don't require me to share my phone number, which is an extremely high priority channel, with everybody I might want to send a message to.

And if it is face2face, scanning a barcode like e.g. Threema supports is even quicker.

[zachlatta]

Right, but Signal is privacy for my dad. He can't remember his email, let alone his email's password.

Different apps for different categories of users.

[detaro]

It would be nice if we could avoid that fragmentation, and to be clear, I am not against Signal offering phone number sync or even making it the default.

I'm not convinced that "just put my phone number 0394859489 in" is so much easier than "I don't have my phone number in there, just type in horse-battery-staple" that not having the second option is a large usability win. Or "give me your phone number and i'll add you" ;)

It's very laudable that Signal tries to be perfectly easy, with as few options as possible, but on the other hand I feel the overdo it in many cases where a slightly more manual, hidden way would help to mitigate issues. If it works for you it's fine, if it doesn't (either through convention or actual bugs, the latter ones are a bigger issue for me) you are out of luck. That's not great for adoption either.