  The paper (Rothleitner et al. 2014 Metrologia 51, L9) reports on the
measurement of the speed-of-light perturbation in absolute gravimeters. The
conclusion that the perturbation reaches only 2/3 of the commonly accepted
value violates the fundamental limitation on the maximum speed of information
transfer. The conclusion was deluded by unaccounted parasitic perturbations,
some of which are obvious from the report.

Instrumentation and Detectors