People frequently send me questions about specific rules of grammar, syntax, and usage. Sometimes, clients will respond to something I’ve written by asking me if I know about a specific rule of language. Both groups are often surprised by my replies.
There really aren’t any rules about writing — just personal preferences that the people who control the writing expect to see.
I’ve written for literally thousands of organizations over the years, and I can attest that each of those organizations has its own writing styles and quirks. A construction that’s perfectly acceptable to one would be viewed as heresy by another.
Some companies actually publish their own style manuals, proscribing specific words or stating how sentences should be constructed. Others point to Associated Press or MLA as their sacrosanct sets of rules. All of those things are just a choice. A preference. So no matter how strongly you feel about the value of the serial comma (also known as the Oxford comma in some circles), know that the company next door may simply abhor it. And you’re both right.