I think the editing in this great film is masterful, if sometimes subtle in its effects. The scene of the lakeside quarrel, when Jack grabs hold of Ennis to comfort him, cutting away to that beautiful flashback sequence, where we see Ennis embracing Jack with such quiet tenderness, is mesmerizing in its elegant mirroring quality. The one embrace, from early in the relationship, marked by optimism and a sense of profound connection, contrasted with the later one, tinged with disappointment and bitterness, overladen with a mood of desperate need. And then how the flashback shot of Jack watching Ennis ride away, with such tender love in his eyes, cuts back to middle-aged Jack, watching Ennis drive away, the years of stifled dreams etched in his lonely face--very powerful, and beautifully done.
I also find Ennis's POV imagery of Jack's supposed murder, contrasted so crisply and bitterly with Lureen's clinical, dispassionate account, to be strikingly effective.