He means size of hands. Children with smaller hands may have trouble with some key combinations.
Thanks. I would have never guessed. Even as a child I had big hands, so... :)
Especially since you need to be young to have any chance to get a positive return of investment with emacs.
I started using it (consistently, all day) with ~22 after learning vi and emacs during my degree (that's 8 years ago). I stuck with emacs for the PhD and now for work, but I'm using evil lately to get text objects. I don't think emacs or vim are that hard, you get used pretty quick to anything you do all day long (I'm now using Acme to write go, as an example of new things)