Be warned! Signaling that you understand signaling is a terrible signal, because it throws all your other signals into doubt.

This is the opposite of true. People want allies that are competent signalers. Explicitly talking about signalling is in most cases a bad idea and usually a signal that you don't understand signalling or respect it sufficiently.

I think there's a distinction between them possessing a generalised skill in signalling and them being engaged in attempting to influence you via signalling. (Consider "He's charming" vs. "he's trying to charm me"). Possibly people resent the implied disrespect in trying to alter their behaviour cia signalling not argument.