You know, the comma before ‘and’ or ‘or’ in a list? It’s the Harvard Comma, and I use it! I was taught to use it, though I was aware that some did not, but I never knew why. Recently, a boss told me not to use it, and I can only assume he has had some training as a newspaperman, or, at least, learned his grammar from someone who was.
The Chicago Manual of Style, Strunk and White’s Elements of Style, most authorities on American English and Canadian English, and some authorities on British English (for example, Oxford University Press, and Fowler’s Modern English Usage) recommend the use of the serial comma. Newspaper style guides (such as those published by The New York Times, the Associated Press, The Times newspaper in the United Kingdom, and the Canadian Press) recommend against it, possibly for economy of space.