If you look a bit more closely you'll see that is not just an article on a website but a wiki powered by mediawiki. As such it is not that suited to design customisation especially the type of design you are referring to.
That being said I would argue this sort of guide or reference is much more readable in a plain unembellished format. Content is king in this instance.
Though I have to admit that I wonder how come most Linux / open source software websites are so average-looking in terms of colors, font and general styling.
There seems to be a policy of content over presentation when it should be possible and even easy to have both in 2011 without much effort.