do you verified in debug that codePostalValidator really adds FacesMessage?
Yes, all errors messages are well displayed, this only the f:facet name="errorMarker" which is not displayed when the error is not of type "required".
So you seems just adding the Message with not ERROR severity.
It solve my problem:
throw new ValidatorException(new FacesMessage(FacesMessage.SEVERITY_ERROR,"error sum","error detail"));