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.
They've repeatedly stated that they're working on removing the need to share your phone number with your contacts, but that's taking some time, because they want to implement it in a way that does not involve storing your entire social graph on their servers.
You'll still have to sign up with your phone number, but the only thing that can be traced back is that your phone number is registered on Signal - and only by subpoenaing Signal, I believe.
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.
They made a mistake in removing SMS support - that was a good way to become useful to people with the current paradigm and encourage them over to the new. Sometimes Signals decisions are self destructive.
I still have signal but I use it much less since it stopped SMS support; I just open it less and so when starting conversations default to WhatsApp. For a while signal was growing amongst my friends and colleagues but it appears to have stalled.
Google are now doing the same pushing their RCS in the default SMS app in Android.
I wouldn't call it a mistake, more like being caught between a rock and a hard place, where Android basically forced them to give up on SMS support even though they'd have liked to keep it: https://community.signalusers.org/t/signal-blog-removing-sms-support-from-signal-android-very-soon/47954/57
But yes, it was really nice when I could use it as my SMS app. Then again, very few people in my country use SMS in the first place - it's all WhatsApp, and it was never able to have support for that. Luckily, most of my friends have adopted Signal by now.
Would I be able to switch seamlessly to another SIM/number in that case, do you think?
I have no idea, unfortunately :/