A serial comma is — and ought to be — called a “serial comma.” Nearly everyone will grasp — or be able to guess — what it is. Clear communication is among a proofreader’s goals.
Do not call it an “Oxford comma,” or a “Harvard comma,” or any other fanciful nonsense. The use of those old school names sounds either pejorative — a suggestion that the thing is old-fashioned — or pretentious. In either case, it will be necessary to explain what you mean, which will be a waste of your time.
