One piece of analysis missing from Macrosticks is how hand size and shape is influencing individuals' preferred hold. The author seems to have an underlying thesis that it's all about how the holder learned, but I don't believe it.

I learned at ~8 and my "ah ha!" moment came when I realized that it was easier to hold chopsticks with my left hand despite writing right handed. Now I can do it well enough with both hands.

My hold is somewhat like the "right hand rule" grip, although the lower chopstick fits into the groove of my thumb unlike the reference photos. And while I've tried other grips — as demonstrated to me by Asian friends — they've never "fit" with my relatively large hands.