  This comment clarifies the relation of the research in a recently published
article [Phys. Plasmas 14, 042503 (2007)] to other prior publications
addressing the inclusion of electromagnetic and drift-kinetic electron physics
in gyrokinetic simulation, raises a concern related to the inclusion of kinetic
electrons in a system with magnetic shear, and discusses alternatives in the
face of an important limitation on the general applicability of the algorithm
described therein.
