> You still need to use your phone number to sign up, though.

Which defeats the whole point. What if the FBI politely asks Signal about a phone number?

I might be misremembering or mixing memories but i remember something about them only storing the hash of the number.

So the FBI cant ask what phone number is tied to an account, but if a specific phone number was tied to the specific account? (As in, Signal gets the number, runs it through their hash algorythm and compares that hash to the saved one)

But my memory is very very bad, so like i said, i might be wrong

They publicly publish these requests. You can see how little information is provided — just a phone number and two unix timestamps IIRC. https://signal.org/bigbrother/