Rebutting fake news on full spectral fitting
  A recent paper by Ge et al. performs a series of experiments with two full
spectral fitting codes, pPXF and starlight, finding that the two yield
consistent results when the input spectrum is not heavily reddened. For E(B-V)
> 0.2, however, they claim starlight leads to severe biases in the derived
properties. Counterintuitively, and at odds with previous simulations, they
find that this behaviour worsens significantly as the signal-to-noise ratio of
the input spectrum increases. This communication shows that this is entirely
due to an A_V < 1 mag condition imposed while initializing the Markov chains in
the code. This choice is normally irrelevant in real-life galaxy work but can
become critical in artificial experiments. Alleviating this usually harmless
initialization constraint changes the Ge et al. results completely, as was
explained to the authors before their publication. We replicate their spectral
fitting experiments, finding much smaller biases. Furthermore both bias and
scatter in the derived properties all converge as S/N increases, as one would
expect. We also show how the very output of the code provides ways of
diagnosing anomalies in the fits. The code behaviour has been documented in
careful and extensive experiments in the literature, but the biased analysis of
Ge et al. is just not representative of starlight at all.
