It's not about forcing anyone to be anonymous. I'm not OP here but I kind of agree. Maybe signal should default to a randomized one with a blurb about safety, anonymity, etc but let you create your own if you want.

Again. My personal view isn't to force random usernames on people but to maybe educate them on this stuff. Also, there are legit reasons why you should have non identifying usernames even if it's not how the world should work. There are enough nutters out there who may recognize something in someones name that links them to someone they know offline and people are nucking futz. I can tell you stories I've heard from my clients that you would believe but don't want to.

Oh and for the numbers, that can be even more identifying because people tend to use numbers that mean something to them. I have a variation on this name that includes my birth year in 2 digits. If I was posting things online that close family might have a problem with, it wouldn't be hard to do to the math and identify me that way.