I happened across an article late last week suggesting I ‘Always Put a Comma Before “and” in a List, No Matter What Your Old Grammar Teacher Said’. I totally disagree. I don’t recall ever having a grammar teacher. I’m certain I hadn’t heard of an Oxford comma before I got my technical writing certificate, well into my thirties. But even the article concludes, “consider your commas carefully.”
The Oxford comma (or serial comma, not to be confused with the Vampire Weekend song) is “a comma placed immediately before the coordinating conjunction (usually and or or) in a series of three or more terms.”. Quite a few popular style guides advocate the Oxford comma, but the last few style guides I adhered to did not, except to avoid confusion. And I firmly believe that avoiding confusion is at the heart of the issue. The Wikipedia page even contains a handful of examples of ambiguous uses both with and without the comma.
A recent lawsuit, brought by a group of truck drivers, hinged on the interpretation of legislation exempting “The canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution” of certain goods from overtime pay. A New York Times article, an NPR Planet Money episode and the above-mentioned Lifehacker article suggest that the missing comma was worth $10 million. While the settlement of the lawsuit was indeed worth $10 million, and the case hinged on the Maine Legislative Drafting Manual advising against use of the serial comma, it was a lack of clarity in the legislation that led to the lawsuit.
My advice is to be consistent with your comma usage and even rewrite your sentence, if necessary, to ensure clarity.