neither did I say it's automatically safe, nor define "safe" as in bug free. The commented I replied to implied that one would walk through the entire stack, e

neither did I say it's automatically safe, nor define "safe" as in bug free. The commented I replied to implied that one would walk through the entire stack, every line of code, to audit e.g. an app running on a phone. This is most certainly not what OP meant. Rather, on a whole OSS is mostly transparent, while proprietary software is not. There are of course bugs, but that's not the focus here with "safety". What we care about is intention. Private companies's have a track record in implementing features that go directly against the benefit if their end-users, e.g. tracking or vendor-lock-in. These anti-features, like the one described in the article, are much harder to detect precisely because the software is proprietary.