A guess:Ennis’s headlong, irreversible fall, precipitated by Ennis’s punching Jack (then spitting)bookended by...Ennis’s collapse at the lake, preceded by Ennis’s (spitting then) shoving Jack
Good one, Fern! I was thinking of the bookend to his headlong, irreversable fall as being when he ascends the staircase at the Twist house. But it's true that in this movie where there's snow, there's something going on.