This is very important, but he's making a deeper point, that the README ties it to the problem it solves. It's possible to make a beautiful, intuitive, natural solution that nobody needs (not even yourself). From the user to the code, it goes:

  problem -> usability -> code

Although intriguingly, pure mathematicians create solutions for their own sake (without reference to a problem), and it sometimes (often?) turns out to have practical application anyway e.g. http://en.wikipedia.org/wiki/G._H._Hardy#Pure_mathematics

BTW: I just noticed you can resize the reply textarea by dragging the bottom right corner. There doesn't seem to be any JS or CSS in the HN source to do this, so I guess it must be in Firefox 9; google says chromium has it too. Seems about 1.5 years old :(