Signal adds a payments feature with a privacy-focused cryptocurrency

Same. It's extremely concerning. Where's the transparency? If the backend has been compromised and turned into a honeypot, how would we know?

That would only compromise metadata as signal is e2e encrypted and the client has always been opensource and up to date.

All the SGX stuff is about making metadata more private for features that absolutely must be done serverside. So a compromise in SGX is more an issue if Signal itself becomes adversarial or gets compromised. Most services only rely on this for security and don't use things like SGX to hide things from themselves.