transvestigator

noun1

1. •
   (Internet) A person who performs transvestigation; someone who routinely conducts or promotes informal investigations into whether a public figure is secretly transgender, generally by analyzing that person's appearance and anatomical structure.

   • No you can't always tell. Of the trans women I've known who told me they were trans I certainly couldn't "tell" when I met them. And the transvestigators just suspect every cis woman. — 2020