The original book and its ilk are akin to programmer code style guides: whether to indent four spaces or two, put the brace on the same line as the if-statement

The original book and its ilk are akin to programmer code style guides: whether to indent four spaces or two, put the brace on the same line as the if-statement or below it, etc. Just as a non-programmer is likely to stare at you, lost, that you would care about whether to use two spaces or four, so we are likely to look at professional typesetters when they wax philosophic about their preferences. But just like all those code preferences, these typographic tidbits have a subtle effect, making a printed page look more professional, elegant, easy on the eyes, etc. As some have pointed out, however, you have to be careful when translating rules from page to screen. For example, Jakob Nielsen was probably right when he said you just leave links alone, let them be blue and underlined. Typophiles especially hate to underline words. They will go through all sorts of acrobatics to decorate links any other way (bottom borders that don't touch the descender thingies on the letters g and y and so forth) or even background images of a line. Thankfully Chrome at least as started to support underlines that by default cross under those descenders. Typophiles also don't care for colored text much and will likely try to color their links black if they could get away with it. Colored text reminds them of children with crayons or their mother making a flyer. Serious type is understated, like a little black dress. I myself am a typophile and come from a background in studying fonts and all that before I got into web design. I have slowly come around to be more like Jakob Nielsen, and I prefer those low-brow unstyled sites by professors and old open-source projects over most "designed" sites these days. But I still prefer a nice serif over sans-serif, and a max-width of about 50em, thank you.