Understanding independent clauses

Question

My understanding is that semicolons are used to separate independent clauses of a sentence, and also to delimit a list wherein one or more members contain a comma.

Regarding the first usage, my understanding is that an independent clause can stand on its own as a complete sentence. Something like "It's getting late; we should head home."

I'm having a bit of trouble squaring that with this sentence from page 1 of Eats, Shoots & Leaves

By all means congratulate yourself that you are not a pedant or even a stickler; that you are happily equipped to live in a world of plummeting punctuation standards; but just don't bother to go any further.

Being a mere computer nerd visiting here from Stackoverflow, I was hoping some of you English gurus could help me understand how "that you are happily equipped..." and "but just don't bother to go any further" can qualify as complete sentences. Both, and particularly the latter seem like fragments.

Answer 1

I think Ms. Truss may be poking gentle fun at the reader there by pushing the boundaries of what you may perceive as correct punctuation; and hoping to get you to think about the subject a little harder. And look: it worked!

Edit: Linking to extra info located in another answer at OP's request in comments.

Answer 2

You provide the useful rule that semicolons may be used with incomplete sentences to delimit a list wherein one or more members contain a comma; but I believe the example sentence you give would be an incorrect application of this (useful) rule.

A practical extension to your rule would be to say that semicolons may be used to delimit a list whose members would be too long to read comfortably if separated by mere commas; I believe this extension is also quite current.

An additional condition would be that, in most cases, there should be at least three members in the list: otherwise the sentence would be easy enough to read with a separating comma instead of a semicolon. The rule is rather meant for sentences like this:

The Russian Revolution indirectly destroyed what hope Old Europe still had of maintaining global dominance, because it eventually led to the rise of the Red Army, which turned Europe into an American protectorate for most of the Cold War; to the focus of European politics on the East-West opposition rather than old colonial ties; to a massive increase in military spending, mostly on nuclear weapons, which deprived European governments of the means to otherwise further their interests; and to a world-wide arms race, which made quick work of what advantage Europe had gained in military technology from experience in both world wars.

Your example does not need the rather forceful instrument of semicolons between incomplete sentences. Even my example might benefit from restructuring rather than semicolons; but at least it is clear that commas would be unacceptable here.

Answer 3

I remember learning about "sentence design patterns" in HS English. What you're seeing may be one of those. These designs are meant to be used when you know the rules well enough to know that you are breaking them correctly, if that makes sense.

For example, compare:

The day was gray, dreary, and sad.

with

The day was gray, dreary, sad.

The "rule," if you will, is that you should have and connecting the last two items in a list, but breaking the rule adds something to the effect that the sentence has on the reader (hopefully a positive one).