  We analyze the results obtained recently by Khazael and Sebastiani (J. Chem.
Phys. \textbf{147}, 194303 (2017)) for two coupled methyl rotors. We show that
one of the avoided crossings obtained by those authors is in fact a true
crossing between states of different symmetry. Present analysis is supposed to
be clearer because it is based on an independent calculation of eigenvalues for
each irreducible representation. The application of group theory also enables a
more accurate calculation by means of smaller matrix representations of the
Hamiltonian operator.
