I totally agreed on his switch on/off Devil Face, not really arguing on that ;)
I was re-watching the whole show because season 4 is coming and I can't wait! I thank you for replying. Love to argue and read, love share passions.
And when I watched the pilot, the priest (during the wedding) was really shaken and can't look away of Lucifer when he approach. He didn't even say his name and the priest was doing his cross sign like I saw the Devil (pun intended, ahah).
Then when I rewatch s1e09, I saw Father Frank staring at Lucifer's face when they met a bit like the priest in the pilot (but yeah way less scared). First Lucifer thinks he's a fraud for asking the Devil's help (and maybe because he don't freak out ?). But Frank is not a fraud and Lucifer realizes he knew and was still being friendly.
For me, Frank knew since first meeting and that make this episode even more powerful to me but it could be like you said, his good judgment/logical ability.
For the preacher divine benefit, it could be a bless for a combined priest and true faith ? like a "see evil" thing ? Yes, sound a bit weird, I agree. And for the benefit being known, I don't know, Lucifer doesn't really walk the whole earth or going to church (like what real priest goes to sex club, night club or else?) so could be a not well known/spread thing.
I don't know maybe I read way too much things in it but that was always the way I saw it (even in my first watch). I was curious because no one else talk about it ;)
Or maybe it's a thing producers throw in season 1 and do not wanted after.
P.S: sorry if I made grammatical mistakes, english is not my first language ;)