  Two approximations used by Sengupta [Phys. Rev. B {\bf 100}, 075429 (2019)]
in numerically computing the adsorption rate of cold hydrogen atoms on
suspended graphene are critically examined. The independent boson model
approximation (IBMA) was used to compute the atom self-energy, and the
single-pole approximation (SPA) was used to obtain the adsorption rate from the
self-energy. It is shown explicitly that there are additional contributions to
the self-energy appearing at the same order of the atom-phonon coupling as the
IBMA terms that alter the value of the real part of the self-energy at low
energies by several orders of magnitude in the regime of interest. This shift
in the self-energy consequently renders the use of SPA invalid.
