Please note that despite much work being done in the equality department being famous is nowadays still a requirement for acquiring the status of impostor syndrome achiever. Persons who are not really famous do not have impostor syndrome but are just a simple copycats in this respect.
So the non-famous people who claim to have impostor syndrome are actual impostors because they claim to have impostor syndrome. Honestly, that seems like a bit of a weird take but to each their own.
