Q. re your Q: “. . . should be modified by the masculine form of the adjective—‘emeritus’—regardless of the professor’s gender.” Let’s stomp this out! “Sex” is not a dirty word! People come in SEXes, not genders.
A. Sorry, but academe tends to disagree with you. “Sex,” while not a dirty word, is considered biological in connotation; “gender” is seen as a social construction. And since CMOS is written mainly for the ivory-towered gang, we acknowledge the distinction.