> Because Signal's client software still is open source.
Only when you can trust that the published client source code is equivalent to the distributed client binaries. The only way to do this is reproducible builds, since building your own client is frowned upon and sometimes actively prevented by the signal people. Signal has always been a my-way-or-the-highway centralized cathedral, no alternate implementations, no federation, nothing. Which was always a suspicious thing. Also, "the signal client is open source software" only holds if you don't count in the proprietary Google blobs that the signal binary does contain: FCM and Maps. Those live in the same process and can do whatever to E2EE...
About the signal client that does the E2EE, reproducible builds are frequently broken for the signal client, e.g.:
https://github.com/signalapp/Signal-Android/issues/11352 https://github.com/signalapp/Signal-Android/issues/13565 and many more. Just search their issue tracker. The latter one was open for 2 years, so reproducible builds were broken at least during 2024 and most of 2025 for the client. They don't keep their promise and don't prioritize fixing those issues, because they just don't care. People do trust them blindly and the Signal people rely on that blind trust. Case in point: you yourself reviewed their code and probably didn't notice that it wasn't the code for the binary they were distributing at the time.
Now you might say that reproducible builds in the client you reviewed weren't affected by their Mobilecoin cash grab, and you are right, but it shows a pattern in that they don't care, and even lots of professionals singing their praises don't care.
And their server code does affect your privacy even with E2EE. The server can still maliciously correlate who talks to whom. You have to trust their published source code correctly doing its obfuscation of that, otherwise you get metadata leaks the same as in all other messengers. The server can also easily impersonate you, read all your contacts and send them to evil people. "But Signal protects against this", you say? Well, it does by some SGX magic and the assurance that the code inside the enclave does the right thing. But they clearly don't care about putting their code where their mouth is, they rather put their code where the money was. Behind closed doors, until they could finish their Mobilecoin thingy.
>> The Signal people are absolutely not trustworthy for reasons of money and greed.
> I don't think you've raised sufficient justification for this point.
Trust is hard to earn and easy to squander. They squandered my trust and did nothing to earn it back. Their behavior clearly shows they don't care about trust, because they frequently break their reproducibility and are slow to fix it. They cared more about their coin thing. They are given trust, even by professionals who should know better, because their cryptography is cool. But cryptography isn't everything, and one should not trust them, because they obviously are more interested in Mobilecoin than in trust. What more is there to justify, it's obvious imho.