  Consequences of different discretizations of the two-dimensional Dirac
operator on low energy properties (e.g., the number of nodes) and their
relations to gauge properties are discussed. Breaking of the gauge invariance
was suggested in a recent work by M. Bocquet, D. Serban, and M.R. Zirnbauer
[cond-mat/9910480] in order to destroy an intermediate metallic phase of
lattice Dirac fermions with random mass. It is explained that such a procedure
is inconsistent with the underlying lattice physics. Previous results point out
that the logarithmic growth of the slope of the average density of states with
the system size, obtained in the field-theoretical calculation of M. Bocquet et
al., could be a precursor for the appearence of an intermediate metallic phase.
