At some point, midway through the procession of holiday dinners at our home this year, the subject of ‘bon appétit’ raised its controvertible head. (Again.) You may not even have known, until now, that it had a controvertible head. You, dear reader, are likely part of the majority of people who merely thought of the phrase—to the extent that you gave it any thought at all—as a festive salutation from the host to “enjoy the meal” and, with this pronouncement, blithely assumed it was the signal to...