Comment on "Irregularity in gamma ray source spectra as a signature of
  axion-like particles"
  D. Wouters and P. Brun in Phys. Rev. D 86, 043005 (2012) claim that an
observable effect in the spectra of distant very-high-energy blazars arises as
a consequence of oscillations of photons into axion-like particles (ALPs) in
the presence of turbulent extra-galactic magnetic fields. The main objective of
this comment is to demonstrate that such a result is physically incorrect. We
also show that a physically correct treatment of the same issue leads to a much
less relevant conclusion, which makes the effect pointed out by WB likely
unobservable with the present capabilities.
