  It is shown that the experimentally observed inverse linear decay of surface
corrugations in Si(001) (Erlebacher et al., Phys. Rev. Lett. 84, 5800 (2000))
is due to the two dimensional nature of the surface in the experimental system.
The theory of one dimensional surface relaxation predicts in this case an
exponential decay, contrary to claims by Ozdemir and Zangwill (Phys. Rev. B 42,
5013 (1990).
