robbo24, page-9

wiki says it's an informal term; rather than oxford's acceptance. Regardless, it's an ingress into the language and I dont accept it as formal English.

I would be offended if referred to as they. 

The English pronoun they is an epicene (gender-neutral) third-person pronoun that can refer to plural antecedents of any gender and, informally, to a singular antecedent that refers to a person.