the goal of the copy editor is to enforce inviolable rules while respecting personal stylistic preferences. this can be difficult, as some writers view grammatical corrections of the copy edited manuscript as a challenge to their intellectual ability or professional identity. for this reason, copy editors are encouraged to side with the author. if the author's preference is acceptable, it should be respected. this practice is complicated further by constantly evolving language conventions as recorded by books on grammar and usage. additionally, the authors of such books often disagree.