signal requires a phone number to sign up. a phone number could be used to trace your signal account back to you. so why do people, especially privacy enthusiasts and experts (like edward snowden), still use it and endorse it when it lacks anonymity in that sense? i get that people could use a voip number or something to sign up, but still.
Btw, the main thing to realise, is that Signal is trying to tread the delicate balance of being accessible and private. If you have the perfect private messenger but nobody uses it, that doesn’t help democracy one bit. So starting out with an easier-to-implement mechanism that also helps adoption (because people can get notified when people they already have in their contact list join), that still protects against indiscriminate mass surveillance, makes sense to me, even if it means your contacts can still know who you are.