The books overall purpose is to focus on content and the SONAR Content Distribution Model. So the nitty gritty of SEO tactics, such as keyword emphasis, was only touched upon and not delved into in detail.
First, a caveat: No one SEO tactic is the end all be all, in and of itself. It is part of a bigger picture using other SEO tactics. So, emphasizing keywords alone will be useless. Several SEO tactics (such as the ones listed on page 116) need to be part of your overall SEO plan.
Second, I'd like to clarify that there are different points of view on this. And I did not go into detail in the book as to use (i.e. sparingly vs. overkill).
However, many webmasters remain to believe that certain tactics, such as alt tags/attributes and keyword emphasis, although aren't critical to overall SEO, certainly don't hurt efforts.
In addition, many webmasters and SEO experts that do agree with subtle use of keyword emphasis think it's 'ok' to underline if another element is used, such as italics, to distinguish from a text hyperlink. Also, it's recommended if you underline text not to use blue font (again, for confusion with hyperlinked text).
Some supporting reading:
http://websguides.com/entry.php?107-To-Bo
http://www.snatchseo.com/boldness_italici
http://www.seomastering.com/seo-forum/htm
http://www.pitstopmedia.com/sem/bold-stro
What do YOU think? Would love to hear your thoughts.