As yopu hopefully have realized now, there is no standard, nor is there even an agreement. I always did Ground pin up because of the idea of something falling on a partially extracted connector. But the other side refers to weight of the cord and/or someone stepping on it to justify Ground pin down so it's the last pin to pull out. I on the other had see people ALL THE TIME who are too lazy to reach down and pull a cord out by grabbing the connector cap, so they yank on the cord itself, and it is always an upwards yank. So that brings me back to Pin-Up.
But my standard joke when someone asks me is, you install it with the U of the Ground pin pointing up, because if it's pointing down all the electrons will leak out onto the floor...
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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