The tag line in the title banner has a comma after “writing.” I thought that last comma before “and” in a list is unnecessary unless “and” is used elsewhere in the list.
For instance, I would use that last comma in a list that includes items like “oil and gas, cake and ice cream, and tractors.” However, I’d omit it a list that includes “milk, eggs and juice.”
The bit of punctuation that’s puzzling you is called the serial comma or the Oxford comma. Supposedly it is sometimes also called the Harvard comma, but I’ve never seen that usage in real life and I suspect some Harvard grads made it up to make themselves feel special.
The serial comma is the one that comes before “and” in a list, and the short answer is, it’s usually optional. In cases where one or more of the items includes the word “and,” like in the example you gave, you need it for the sake of clarity. It’s also often a good idea in sentences where the items listed take more than a couple words to describe. For example:
Julie went for a run through a little-frequented corner of the park, came home to whip up a batch of homemade granola for her kids’ soccer team, and retired to the garage to weld the enormous metal sculptures critics had called “nightmarish yet strangely erotic.”
The items in this list are long enough that without the comma, a reader can’t be sure at first whether the “and” will be a continuation of the current item—for example, “for her kids’ soccer team and ballet class”—or the introduction to the last one. The comma makes it clear.
In short lists, like the one in my header—”grammar, usage, style, writing, and editing”—the comma isn’t really necessary, but it isn’t hurting anything either.
This is where style guides come in. Some of them advocate using the serial comma only when it’s needed for clarity, not in simple lists. The AP Stylebook is in this camp, and part of the reason is that in newspapers, where text runs in narrow columns, a single comma can easily bump a word down to the next line and make a paragraph longer. Using a comma-light style may not make every story shorter, but it will make some shorter, which means they need less space, less ink, and less paper.
Other style guides, like the Chicago Manual of Style, say writers should always use the serial comma. Advocates argue it’s a no-muss, no-fuss rule, as it doesn’t require writers and editors to examine every sentence to see if it contains any ambiguities that could be eliminated by the serial comma. They also argue that when everyone gets in the habit of adding that comma in all cases, fewer embarrassing ambiguities will slip through. The famous sample sentence everyone gives when arguing for the routine use of the serial comma is this:
I dedicate this book to my parents, Ayn Rand and God.
Whoops! Are her parents Ayn Rand and God, or was she trying to dedicate the book to her parents, and Ayn Rand, and God? If the writer were in the habit of always using the serial comma, this wouldn’t happen.
The counterargument is that even with the serial comma, certain ambiguities will crop up, and editors will just have to watch for these no matter what comma rule they follow. Here’s another example:
Whoa now! For want of a comma, we’ve turned Nelson Mandela into an ancient demigod and sex toy enthusiast. But wait a sec, what happens if you add the comma?
Nelson Mandela, an 800-year-old-demigod, and a dildo collector
OK, um, Mandela might still be a demigod, according to this sentence. I guess that 50% less hilarious libel is an improvement, but to really solve the problem, you’d have to rewrite the sentence.
So habitually using the serial comma certainly doesn’t solve all problems of this sort, but it does take care of some of them, like in the Ayn Rand example. And not having to think about whether a sentence needs a comma is nice. And, irrationally, I just kind of like the serial comma. Which is why in the header, and in this blog, I tend to use it.
But at work I use AP style, so I don’t always use the serial comma. And as for you, if you write for a living, do whatever your style guide tells you. If you’re not a writer, use it or don’t. Either way is fine.