On its 10th anniversary, Signal’s president wants to remind you that the world’s most secure communications platform is a nonprofit. It’s free. It doesn’t track you or serve you ads. It pays its engineers very well. And it’s a go-to app for hundreds of millions of people.
They probably have turned over logs because legal persuasion, and it sounds like they anticipated that. Moxie has been around the cypherpunk scene for a while, so they knew what they’re doing.
Plus the paper on the double ratchet algorithm is out there. https://en.m.wikipedia.org/wiki/Double_Ratchet_Algorithm