SPOLIER SPOILERS SPOILER IN RE: IN A LONELY PLACE
In a Lonely Place is all the better for it's almost murder; if Dixon had actually killed Laurel, it would have been just another violent crime movie ending.
The film is more tragic because Laurel lives (saved by the telephone call that "would have meant so much" if it had come just a few minutes earlier), letting the horror of what might have happened, and what was almost certainly going to happen, sink in for both Dix and Laurel.
Obviously there is no way Laurel can stay with him after that.
It's profoundly sad - the two of them going their separate ways, knowing that they "lived a few weeks while they loved" each other, but that the happiness they had during those few weeks could never return.
As for the idea that the film would somehow be more noirish if Dix had succeeded in actually strangling Laurel, I say, the idea of murder in film noir is over-rated. There are actually quite of lot of noirs in which murder is not the main event.
I respect your argument, but I am still willing to die on the hill for the ORIGINAL ENDING to IN A LONELY PLACE.
Had I been on-set, I would've gotten into a violent argument with Ray, thrown pages in his face, and knocked over the craft services table as security hauled me off the Lot as I shouted a vocal, expletive-laden defense of my cause...