  In arXiv:1202.0691, Geloni et al. criticise our recent work describing the
spontaneous emission by a relativistic, undulating electron beam. In particular
they claim that our prediction of a quantum regime in which evolution of the
electron momentum distribution occurs as a sequential population of discrete
momentum groups rather than in terms of a drift-diffusion process is unphysical
and artificial. We show that the criticism of our model contained in
arXiv:1202.0691 is unfounded.
