I was already well aware of it's long historical usage, I simply would only rarely see someone say "Chaucer used it, therefore it's fine to use on a resume!" The spelling "aks" for "ask" is one such example that you could find nearly as many high profile historical usages, and no one argues that it is an acceptable spelling.

(Also half that list is exactly the kind of people that you would find an enormous amount of nonstandard usages; Chaucer is Middle English, Shakespeare was famous for writing in common vernacular, Lewis Carroll is famous for his literary nonsense and wordplay; hardly the best sources for what would be included in 'high' English)

English is defined by usage; Singular they has very widespread use from the time of Chaucer to the present day. Only mad grammatical prescriptivists object to it :)