  In a recent paper [I. Brevik, Phys. Rev. A 98, 043847 (2018)], Brevik
analyzed the experiment by Kundu et al. [A. Kundu et al., Sci. Rep. 7, 42538
(2017)] reporting deformation of a graphene oxide (GO) film after it has been
irradiated by a laser beam. The two-dimensional atomic force microscope (AFM)
line scanning of the deformation of the GO film after switching off the laser
beam takes by far too much time for any elastic changes to remain in the AFM
scans. Thus, the changes in the GO film are irreversible and the optoelastic
model used by Brevik is not applicable. The rough estimates of the kinetic
energy and displacement of atoms by the optical force of a light pulse
calculated by Brevik are correct, but in making a comparison with the
corresponding high-precision results for the kinetic energy and displacement of
atoms in our work [M. Partanen et al., Phys. Rev. A 95, 063850 (2017)], the
kinetic energy of atoms is confused with their rest energy. The atoms and their
masses are displaced forward by the field and their displaced rest energies
give rise to an energy flux. The difference of arguments between ours and
Brevik's culminates on the question whether the flux of rest energy caused by
the displacement of the medium moving with light should be included in the
total energy flux. We also show that the four-divergence of the
stress-energy-momentum tensor of the mass polariton theory of light is zero.
