In general, signal has proved they store no data besides the phone number itself, and in court they have only been able to give phone numbers.

My problem with signal is actually this, because it's only part of the story.

Let's say the FBI suspects you of doing something horrible, like say you played baby shark in public. They have good cause to believe you're a Signal user, so they get a judge to authorize a subpoena based on your phone number, and Signal complies - and, yes, all they're doing is confirming to the FBI that you have an account with them.

Now they're going to go after you with 'We know you have a secret messaging app you use, Signal, and we know you used it to plan playing baby shark at the mall last Tuesday.'

And so, if you're not really clear on how all of this works, it's a fantastic wedge to try to pry actual incriminating information from you. Or, hell, you let them look at the app on your phone negating the whole damn encrypted part in the first place, because you're sure they already know.

Properly secure messengers shouldn't be tied to that level of PII, because, well, cops can still try to use it to bludgeon you.

Maybe a little paranoid, but I've decided to embrace some of the paranoia since not doing so means you have to trust in the rules and policies that the law puts in place and well, uh.....