[throwaway8879]

Signal still requires a phone number. That alone should make it non-usable for people who are serious about their privacy.

My alternate solution: stop using smartphones altogether. Technology is not a good solution to the privacy problem, especially when a collective such as the government can read your data anyway, or beat it out of you.

If you're worried about drowning, don't go near water. There are no fullproof life vests.

[icebraining]

What's the "privacy problem"? I suspect yours is different from many other people's.

[Mediterraneo10]

In many countries (an ever-expanding list), you cannot purchase a SIM card without showing ID, and a copy of your ID is made and sent to the state authorities. That is, mobile numbers are always connected with your identity, you cannot have an anonymous phone number. Consequently, the state can easily determine which of its citizens are using Signal.

While communications on Signal are end-to-end encrypted, in authoritarian states merely using a secure messenger can draw police suspicion.

[jtl999]

Some people might not want to give a phone linked to them to certain people while attempting to remain anonymous.

I don't disagree this is less then the userbase of Signal, but I assume it shouldn't be hard to use a randomly generated ID (or similar) system as a fallback options for identifiers, and leave phone numbers as the default and recommended setting.

[anigbrowl]

That's a good point about privacy, but then you're throwing the baby away with the bathwater, since all your secure communication now requires you to operate a laptop at the very least. You'll have more privacy, but significantly less operational capability (ie to communicate with your friends while walking around).

[pergadad]

Phone number is convenient to find people and uniquely identify them with a standard info that you have anyway for most friends. If not for the phone-based account I'd have missed that many friends do already have signal.