  Understanding the physics of beam-plasma systems is of great importance for a
large number of astrophysical systems. Recently the validity of
particle-in-cell simulations of these systems has been questioned by Shalaby et
al. (2017) We analyse one specific beam-plasma and its numerical simulations
Kempf et al. (2016) that has been critized and prove that in fact the
simulations performed fulfill the new validity criteria introduced by Shalaby
et al. (2016).
