i disagree singular they their has been used by educated people in a formal register for a long time in fact i have a copy of a british passport application that uses it in that sense i prefer it sometimes and intend to keep using it grammatical rules are fluid and prescriptivists who think they are not can have a stifling effect on discussions and even distort people's perceptions of some groups within a society based on some perceived error in the way they speak for an encyclopaedic style all that matters is whether a significant number of educated native speakers would find a particular usage acceptable proscriptions on split infinitives terminating sentences with preposition and other poor grammar are for another age aug utc