  In their recent Letter (Phys. Rev. Lett., Vol. 93, 106406 (2004)), Katanin
and Kampf reported numerical results for the self-energy Sigma(k;e), at real
values of e, of the single-band Hubbard Hamiltonian in two space dimensions,
obtained through employing the functional renormalization-group (fRG) formalism
at the one-loop level. Several of the results by Katanin and Kampf are in full
conformity with the exact formal results reported earlier by the present
author. This, as we shall elaborate in this contribution, strengthens one's
confidence in the reliability of the fRG in dealing with models of
strongly-correlated fermions.
