Another question: why shift your right hand one place to the left from its normal position on the home row?

The first answer in the OP gives a pictorial reference for this.

I would prefer JKL; to HJKL because my index finger typically rests on the J. Then again, I am an Emacs user, so what do I know?

As you get more experienced in vim, you learn more powerful ways to jump around horizontally on a line (t/T/f/F, word navigation, incremental search, etc.), so the most common granular cursor movements become down and up -- which conveniently map to the home-row keys under the strongest and second-strongest fingers.

Right, that makes sense. In Emacs I generally use C-n (next-line) and C-p (previous-line), but for horizontal movement it’s usually thing like M-b (backward-word) and M-f (forward-word), or C-s (isearch-forward) and C-r (isearch-backward). Emacs isn’t really as good at raw text editing as vim, but clearly there is a lot more to Emacs than raw text editing.

This is exactly why I don't use HJKL for navigation in vim. Shifting my fingers causes me to mis-type all the other commands. I end up just using arrows or word navigation.