And as someone (sorry forget who) pointed out, Ennis is smoking outside Aguirre's trailer earlier so his asking for Jack's lighter at the bar is unnecessary and is his first kinda flirty thing.
Not necessarily. I'm a smoker. Lighters are just more convenient than matches. If I had matches and any other person a lighter, I'd ask for the lighter, too. Or if I had my matches (or lighter) somerwhere in my pockets, but the other one has it handy or on the table or is toying with it, I'd take the other person's instead of pulling mine out from the pocket. Lighters and matches are
always in the last pocket you look. I wonder how many hours of his life a smoker spends with looking for lighter/matches
.
So Ennis asking Jack for the lighter is maybe unnecessary, but is sure a complete ordinary occurrence. That doesn't exclude the possibility it is indeed a flirty thing. But it could just as likely be not a flirty thing.
On a sidenote and off-topic on this thread:
What I find far more remarkably at the bar scene is that Ennis tells Jack the story that and how his parents died without being directly asked.
Do we ever actually
see Alma smoking? I think not.
After J's&E's night at the Siesta, it would have been logical to see a full ashtray in front of Alma at the kitchen table, presuming she sat there half the night (or longer).