At some point, he got some hand injury that meant he couldn't type normally for months. He would only have been 21 or 22.
This scared me, so since then I've followed the standard advice on avoiding computer-related injuries very carefully. I use a desktop computer with an external, adjustable monitor. I use ergonomic keyboards, and use a mouse with either hand. I learned to touch-type with the Dvorak layout, I have an adjustable desk, etc.
I haven't had any problems, and I don't know which (if any) of these actions helped, but I'm surprised when I see other developers apparently happy to hunch over a laptop keyboard for 8 hours, while sitting on an awkward chair in a coffee shop. Why do this to yourself?