All types of predicate constituents do not agree alike with polite plural pronoun subjects; if the referent of the polite, formally plural pronoun is singular and any predicate type shows plural agreement with it in the language, it will be the verb; and if any predicate shows singular agreement with, it will be the predicate noun, as Comrie* pointed out.
Standardized
Whenever predicates agree with subjects in number and there is a politeness contrast for pronouns of address, with plural forms serving as polite singulars, IF any predicate constituents other than verbs are plural in agreement with polite plural (referentially singular) subject pronouns, THEN verbs are also plural; IF any predicate constituents other than nouns are singular, THEN nouns are also singular.
Keywords
agreement, politeness, number, plural, singular, personal pronoun, predicate noun, verb
Reference is to:Comrie, B. (1975). Polite plurals and predicate agreement. Language 51: 406-419.See #1066.