Comment on "Black Holes are Neither Particle Accelerators Nor Dark Matter Probes"

The Banados-Silk-West effect consists in the possibility to get infinite energy in the centre of mass frame of two particles colliding near the black hole horizon. According to S. T. McWilliams, Phys. Rev. Lett. 110 (2013) 011102, the energy at infinity of the outcome vanishes because of infinite redshift when the point of collision approaches the horizon. I show that this is not so.