Serial comma and ampersand
Today, I saw multiple people say that even if you use a serial comma before and, you shouldn’t use one before an ampersand. That is, even if you write A, B, and C, you should write A, B & C.
I had never encountered that idea before, and I was very dubious about it. But I checked Chicago, and found out that they agree:
Though the serial comma has officially been Chicago style since 1906 (when the first edition of the Manual was published), we prefer to omit it before an ampersand (see CMOS 6.21). The serial comma—the one before the conjunction in a series of three or more (it’s also known as the Oxford comma)—suggests thoroughness (some consider it to be unnecessary); the ampersand, by contrast, is an abbreviation (derived from the Latin word et, or “and”). The two together, then, make for an odd pairing of the thorough and the minimal. Either remove the comma or spell out the word “and.”
I still strongly disagree. To me, the serial comma isn’t about thoroughness or maximalism or formality; to me, it’s a way to separate items. (When I read A, B and C, it feels to me like that’s grouping B and C together.) So to me, using a comma before and makes sense regardless of how and is written.
But still, I’m fascinated to come across this rule that I’ve never heard of before but that’s well-established and endorsed by a major style guide.