Hell, it doesn't even have to be accidental if Zir doesn't tell Eighis what he's doing. Unless there's, like, voices in his head or something, Eighis would not be able to tell if his mind or feelings are being read. He blocks people from reading those, but he has no way of detecting if it's being done unless someone tells him. (If Zir was trying to alter his mind in some way, it'd be a different story.)