There's also a bit of Fitt's Law in here as well - I find it a lot harder to select, or put my cursor in, a single letter variable. So if I want to rename `i` to something else, I must carefully select `i`, whereas with a longer variable I find it easier to put my cursor in the middle of `index` and hit F2.
I started using ii as my iterator variable name for similar reasons. Easier to highlight and Ctrl-F for. Also removing ambiguity when using i as the imaginary constant.
