Laura, I have also heard the idea of reducing "feeding aggression" by feeding in a separate container. In other words the idea was that the snake would be less likely to grab your hand, if they didn't get fed in their cage.
I have found in my limited experience (with corns and gray-bands), that this is not a problem. When my snakes have grown up, and it became more convenient to feed in their cages, they have not acted like they were going to bite when I reach to pick them up. I usually present them with the flat of my hand, instead of poking a finger in their faces, HaHa!
I do like to feed hatchlings while holding them, just because I think its fun.
I just remembered an exception that happened this summer. I reached in to offer a small cornsnake a pinky, and didn't use tongs. He was VERY hungry, and struck, missing the pinky and grabbing my thumb instead. He immediately wrapped around my thumb to "kill" it, and every time I wiggled it he tightened up more.
I was laughing so hard, and went to show my wife in the other room, that I forgot to grab the camera until it had let go. As soon as it let go, I offered it the pinky again, and it ate while still wrapped around my thumb.

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Kent