  In a recent paper Roux [Phys. Rev. A 79, 021608(R) (2009), arXiv:0810.3720]
argued that thermalization in a Bose-Hubbard system, after a quench, follows
from the approximate Boltzmann distribution of the overlap between the initial
state and the eigenstates of the final Hamiltonian. We show here that the
distribution of the overlaps is in general not related to the canonical (or
microcanonical) distribution and, hence, it cannot explain why thermalization
occurs in quantum systems.
