NOTE although I have said this in comments already: The Coen brothers are not responsible for this dialog: it is in the original book and movie.
To me an extremely striking feature of the movie True Grit is at almost every meeting between characters is that whether they are strangers or even enemies, almost friendly chitchat occurs between the characters.
Perhaps the most extreme example is when Mattie comes upon the hired man who had murdered her generous father unexpectedly. Not only is Chaney almost happy to see her but helpfully tells her she must cock her pistol as she has it pointed at him and this results in his being shot. The talk continues even after he is wounded. Part of this can be attributed to his amusement at this small girl aiming at him and as he says, I did not think you would shoot me.
There is also the conversation that Pepper and Mattie have, where Pepper jokingly talks about that same pistol misfiring.
There is also the overly-familiar and creepy conversation between LeBoef and Mattie where, in her room alone with her, he discusses having considered sexual assault -- later he does assault her (a spanking, pretty darn familiar -- he is a young man and she is 14 -- some sexual overtones).
If I think of it, these interactions happen in every single case as far as I can recall.
I am wondering if the author or reviewers discussed this -- my idea is that in those days and especially on the frontier, company and conversation were the primary entertainment and people did not let a little thing like mortal enmity interfere with this.
If this idea is true, do we find similar sudden familiarity in other stories of the old west?