  The recent paper of Lieu and Hillman [1] that a possible, (birefringence
like) phase difference ambiguity coming from Planck effects would alter stellar
images of distant sources is questioned. Instead for {\em division of
wavefront} interference and diffraction phenomena, initial (lateral) coherence
is developed simply by propagation of rays (cf. van Cittert-Zernike theorem).
This case is strongly immune to quantum gravity influences that could tend to
reduce phase coherence. The phase ambiguity, if actually present, could reduce
any underlying polarization of the light rays.
