  The spacetime of Ho and Weiler [Phys. Rev. D {\bf 87}, 045004 (2013)]
supposedly admitting closed timelike curves (CTCs) is flat Minkowski spacetime
with a compactified coordinate and can only contain CTCs if the compact
direction is chosen to be timelike. This case of a "periodic time" is probably
the simplest example of a causality-violating spacetime; it trivially satisfies
all energy conditions usually assumed in general relativity, and its geodesics
are just straight lines. Its relevance for phenomenology of the LHC, on the
other hand, depends on consistency with observational constraints on gravity,
as is mentioned in general but not discussed in any detail by Ho and Weiler. We
verify a basic consistency check for stationary sources.
