The links to LibreSignal (already mentioned here) and Wire stories summarize most of what I was pointing at: https://github.com/LibreSignal/LibreSignal/issues/37#issueco... https://medium.com/@wireapp/axolotl-and-proteus-788519b186a7
I haven't looked super deep, but to the best of my knowledge that's not something that happens really. I looked through that reddit thread (thanks for that BTW, whisperfish seems interesting) and skimmed over that enormous GitHub thread, but I couldn't find much in the way of people actually experiencing issues interacting with the Signal server. Again, would appreciate it if you could link me to such a thing. As I mentioned elsewhere, I maintain an unofficial signal client and I try to be aware of these sort of things.
Is the policy enforced? I've seen no evidence of it.
Other things that are being brought up here are at least as important and interesting to discuss.