If that had happened, Jack and Ennis would have ceased to be Jack and Ennis, and would have become two entirely different people.
I guess you mean the same thing that I meant with saying the story/movie would not have worked the way it does. Would have been a whole different story.
So it might be nitpicking, but I don't agree with your wording. People can act in different ways, with different outcomes and those outcomes have repercussions on the person. But that doesn't mean the person will be an entirely different person.
I'm always best in explaining with simplifying examples: imagine you were offered two jobs: one in Alaska and one in Florida. No matter which one you will take, it will alter your enviroment, your social contacts, your lifestyle. But you wouldn't stop being Mel and become an entirely different person.
Some things would change, but not your whole personality.
It was a tipping point, definitely - more than at any point in the story, that's the point at which I can most imagine things ending differently.
For me it's one of the two points. The second one for me is after their lakeside confrontation. If Jack hadn't died... I'm one of those who believe Ennis had it in himself to come around (and still be Ennis). I think he was on a good way. Since we've discussed this already, I just mention some keywords: the way their argument shook him to the core, dumping Cassie, admitting that he can't stand it anymore not only to himself, but also to Jack, trying once more to get days off in August, his look in the diner (pie-scene) after Cassie leaves.
Of course I speak of movie Ennis here. For story Ennis, we can only rely on Annie's word's: torqued things to almost were they had been...nothing ended, nothing begun, nothing resolved.
But on the other side, SEnnis, just like his movie pendant, was so terrified by Jack's word's that it drove him to his knees, he looked like heart-shot.
It's harder for me to imagine what might have been (if Jack hadn't died) for the short story.
But the relationship had a delicate balance to it, and by the time of the divorce, I think the nature of the balance was clear to both men. In the story, a phone call might have been so unusual that it made Jack think that the balance had been altered. The movie doesn't explain how the postcard made Jack think things were different, but something must have. But the balance hadn't really changed.
(I kind of see the punch at the end of the summer as an example of what happens when the balance is disturbed. Not that Ennis is inherently violent or anything like that, and not that Ennis would have punched Jack again. Just that Jack knew that Ennis had a low startle point, and Ennis might have thrown Jack once, but he wasn't going to throw him again.)
The balance = their pact = not queer, not in love, only friends with additional benefits ("this thing", that grabs hold of them); and therefore a couple of HAF are enough. And, also important to their pact (for the balance): don't ask, don't tell, go on pretending.
Pretty fragile this balance. Each and every good-bye must have told both of them another truth.
