I'm actually surprised that either so many people really have no actual hands on experience with snakes, or are just not very observant.
BABIES will learn QUICKLY about being fed. I had a regimen whereby I would clean all the babies due to be fed that day the first pass through, then when the frozen/thawed pinks were ready, I would then go through and feed them all on the second pass. Even the aggressive feeders very quickly picked up on this, and knew not to bother getting excited about being fed till the SECOND TIME I opened up the deli cup lid.
As for breeding for temperament, OF COURSE you can. That's exactly what I had been doing for generations. I would always tend to keep the calmest animals and rapidly weeded out any that seemed resistant to handling or captivity in general. Connie did the same thing with her leopard geckos and had then where they were literally puppy dog tame. She selected the "keepers" for personality over any other criteria, because they were pets to her. She selected ones that not merely tolerated handling, but actually seemed to enjoy and prefer it.
Heck, for that matter, why do you think snakes generally tend to become more mellow with age? Well, do you think, perhaps, that they have LEARNED that YOU are not a threat to them. What do you think "scenting" really is? It's getting a snake to LEARN that the smell of something they don't initially want to eat is actually FOOD.
Surely most of you have noticed that every snake has it's very own personality?
No, you will never be able to train a snake to go fetch the newspaper, but they most certainly DO have the capacity to LEARN about their environment and act upon that knowledge.
Heck, for that matter, I'm having sort of a running battle with a wild gray rat snake around here. He wants to be in the bird feeder near the house, and I really don't want him eating our birds. So I just pick him up and carry him off to the far reaches of our property and release him. I've done this about a half dozen times now. I know it's the same one because of a unique marking on the side of his neck. At first he was quite nervous about being handled, but after the third time, it's now old hat to him. He has LEARNED that I am not going to harm him, and he just gets a free ride off into the woods. Now I will take him to a different place each time to release him, even spinning him around in circles to try to disorient him, and he STILL finds his way back to the bird feeder. He just KNOWS where he wants to go. Might take him a few days, but he seems to be able to figure it out.