Copy editors are meant to be gnomes working invisibly below-decks to ensure that the engine of prose runs smoothly. They shouldn’t obtrude themselves conspicuously into the middle of a clause, so that the reader has to break off his attention to the writer’s argument and do a little mental stutter-step before he can remark to himself, Oh, I see—it’s that data-must-be-plural business.

—Geoff Nunberg, Language Log