For example, if I read a comment from which I know, that an ordinary commoner doesn't know, even if they is a professional. For example, if somebody on the Space SE writes something which is unlikely to be known anybody except internal employee of the NASA, possibly astronauts. Or, if somebody identifies himself as a Nobel prize holder on the Physics SE1.
I think the logical behavior would be to silently trying to tune the things into a direction where their appearance serves the best of the site. However, I am only a small fish there.
So, what to do? Mod flag?
1 This question is for the case if the nick doesn't reveal himself. In the known PSE case the Nobel prize holder used his own name.