Q. In the following sentence, is a comma necessary after the word “was”? Her reply was “No, but I’ll think about it.”

A. When a verb like “said,” “stated,” “wrote,” or “replied” introduces a quotation, a comma usually follows the verb: She replied, “No, but I’ll think about it.” (“She said” and the like are sometimes called speaker or dialogue tags.) This comma is a matter of tradition rather than logic, because a comma isn’t usually needed between a verb and its object or complement: she said nothing; her reply was final. In your example, because “be” and its forms aren’t thought of as traditional dialogue verbs, a comma isn’t needed after “was” (though some writers and editors will prefer to add one for an appearance of consistency). See also CMOS 13.14 and 13.15.