Actually what hes done in the example works a bit more subtly than his description. The brightness of the comments (yellow) is similar to the background (white), which allows you to read the code by itself (squint and the code stands out, whilst the comments fade into the background). The same thing wouldn't work nearly so well if, for instance, you had white text on a black background (with yellow comments).
I'm a big fan of comments having a different background color. My code windows are black background, and comments have a very dim magenta background tint to them (with bright green or yellow). I find it relatively easy to either focus on the comments, or ignore them, this way.
