Not that either of them actually feels anger at this point -- they're both dying to stay together longer or at the very least to express their real feelings. But I think the shadow of the earlier fight and punch is still hanging over them and is part of why they can't say anything, or at least part of why Ennis can't say anything (he feels guilty).
Thanks for explaining. Now I see your point and agree.
moremojoI just reflected on the fact that the two don't shake hands in goodbye at their parting, which would have been a socially licit form of physical interaction between them down from the mountain, and would have given them a last parting touch
At the risk of sounding like someone else

: In the story, they shook hands and hit each other on the shoulder.
A possible explantation for the difference between this scene(s) in the story and movie:
I think this scene was altered in the movie because movie-Ennis was different from story-Ennis.
Movie-Ennis is very sensitive to sensuous things: light, tactile things, scents (we talked about it a few days ago, someone else pointed this out - Amanda?). Ennis can't stand Jack being tender to him after Jack accidentally hit his nose and being touched in order to be comforted. Ennis breaks totally and literally down when Jack holds him at the lake scene. Ennis can't help himself but kiss Jack passionately when hugging him at the reunion scene (ok, the four years have mattered, too

).
So a handshake or a hit on each others shoulder may have been too much for movie-Ennis. Either his breakdown would not have taken place in the alley, but right in front of Jack. Or, to avoid that, he would have rebuffed Jack again.