I worked on three OTF-funded security audits a few years ago (though not of Signal). No spook crossed my radar at any time. I'd have been very surprised if any had tried to pressure us at that work; you can read Bamford or the Snowden stories to get a better idea of how they seem to work.
(Despite having some security experience I'm not a cryptographer, and I feel kind of silly speaking up here. But the FUD is even sillier.)
(Despite having some security experience I'm not a cryptographer, and I feel kind of silly speaking up here. But the FUD is even sillier.)