But we have to trust that Moxie is running the server software he says he is. We have to trust that he isn’t writing down a list of people we’ve talked to, when, and how often. We have to trust not only that Moxie is trustworthy, but given that Open Whisper Systems is based in San Francisco we have to trust that he hasn’t received a national security letter, too (by the way, Signal doesn’t have a warrant canary). Moxie can tell us he doesn’t store these things, but he could. Truly secure systems don’t require trust.
We have at least one data point that says that Signal stores exactly two integers about you, or did when the subpoena was issued: https://www.aclu.org/open-whisper-systems-subpoena-documents
things can always change, but that’s evidence submitted in court under the penalty of perjury, which is a fairly strong claim.