I conclude this series on misinterpretations of my teaching with the Oxford comma, or serial comma, a punctuation mark I invariably use but do not insist that others do. I could have ended the post with that single sentence, but, hey, I'm a writer.
Notice the comma, known as the Oxford comma, before and in the following sentences:
Thanksgiving has passed, Christmas is coming, and New Year's Day will soon follow.
Billie Holiday, Charles Mingus, and Duke Ellington were born in April.
Rita Dove has written poetry, fiction, drama, and essays.
I have evidence of using this comma when I was a college student in the 1970s. I have no logical reason for using it; it is just a preference. I have seen many examples from teachers trying to prove that using the Oxford comma adds clarity to a sentence, but all those examples would be better rephrased with or without the Oxford comma for clarity. I tell my students that they may use it if they wish and I will not correct them if they do not, but I do suggest that they do or do not use it consistently. When my editorial clients ask me why I use it, I say it's just a choice. Then some will tell me to drop it, and most will tell me to keep it and adopt it themselves. I do what my clients say on this matter. They are the ones who pay the invoice.
Consistently use the Oxford comma if you like, but I did not say you must.