  Recently, Chen \em et al \rm.\ [Phys. Rev. A 84, 033835 (2011)] reported
observation of anticorrelated photon coincidences in a Mach-Zehnder
interferometer whose input light came from a mode-locked Ti:sapphire laser that
had been rendered spatially incoherent by passage through a rotating
ground-glass diffuser. They provided a quantum-mechanical explanation of their
results, which ascribes the anticorrelation to two-photon interference. They
also developed a classical-light treatment of the experiment, and showed that
it was incapable of explaining the anticorrelation behavior. Here we show that
semiclassical photodetection theory---i.e., classical electromagnetic fields
plus photodetector shot noise---does indeed explain the anticorrelation found
by Chen \em et al \rm.\ The key to our analysis is proper accounting for the
disparate time scales associated with the laser's pulse duration, the
speckle-correlation time, the interferometer's differential delay, and the
duration of the photon-coincidence gate. Our result is consistent with the
long-accepted dictum that laser light which has undergone linear-optics
transformations is classical-state light, so that the quantum and semiclassical
theories of photodetection yield quantitatively identical results for its
measurement statistics. The interpretation provided by Chen \em et al \rm. for
their observations implicitly contradicts that dictum
