Copyediting . . . requires attention to every word and mark of punctuation in a manuscript, a thorough knowledge of the style to be followed, and the ability to make quick, logical, and defensible decisions. . . .

A light editorial hand is nearly always more effective than a heavy one. . . . An author’s own style should be respected, whether flamboyant or pedestrian.

– Chicago Manual of Style 2.48, 2.51