Why have such a chapter in a book on grammar? After all, punctuation is normally considered a discrete skill: in the main it orchestrates meaning rather than defines it, and that's why I haven't included a separate chapter on 'ordinary' punctuation. 1 However, we have already seen a number of instances where punctuation does influence meaning, and that is regularly an issue when it comes to punctuating speech and quotation.
A second consideration is that these skills are extremely tricky, even for fully competent writers. Contrary to many students' beliefs and practice, punctuating dialogue or quotation is not just a matter of providing inverted commas at appropriate places: all the other 'normal' punctuation skills remain in play as well. This means that at any one time there is a great deal to remember, a great deal to get right; and if those 'normal' skills are not fully assured, any attempt to deal with more sophisticated tasks is very likely to dissolve into chaos. And that apparently forbidding observation leads me a third reason for including this chapter. For I have found it be an almost invariable law that
Anyone who can punctuate speech and quotation correctly is entirely competent not only in all other aspects of punctuation but in all significant matters of grammar as well.
In other words, if you can master this section, you can master anything.
1 Those who might require such a guide are referred to Part Two of the revised (2002) edition of my Write In Style.