I was also disappointed that some of the lines from the story did not make it into the movie - especially the "g.g.o" from FNIT and the "little darlin'" from the Reunion scene. It seemed in the story that Ennis was just so much more verbal in his love for Jack, and I at least felt better for Jack - because in the book he had verbal confirmaton that Ennis cared for him and thought of him while they were apart.
However, I can understand that for Annie Proulx the only way she could convey Ennis' emotion and thoughts was through the written word. Whereas, in the movie the actors, set, lighting, music -- all of it can come together to convey thoughts, mood, etc. In another thread someone posted Ennis' little head nudge during the reunion scene was his "little darlin". I read that, and thought, "Yes! Okay, I don't feel so bad about missing that line, now." I think, although both the story and movie can enhance our understanding of this love story, they need to stand alone as separate works of art.
As for the discussion about the Thresher, I remember thinking how brilliant of Proulx to have them talking about, not just a current event item, but also analyzing it - expressing their opinion to each other. It creates a level of intimacy and trust. For anyone that's ever been camping, it just brings up that image of sitting by the campfire, watching the flames illuminate each other's faces, listening to the crickets, surrounded by dark sky and stars and that awesome feeling like you're the only two people in the whole world. The quiet tone of the other person's voice because you don't want the sound to carry, and the feeling like you can talk about anything and BE anything. I never read more into it than that but I appreciate the insights expressed -- more to think about.