  Recently, an alleged plausible astrophysical scenario was proposed for the
production of observed thermal gamma-ray bursts, via Hawking radiation emitted
from a primordial black hole (PBH) freely falling into a more massive black
hole. Here the implausibility of that scenario is demonstrated, and the key
flaws in that paper's calculations and assumptions are elucidated through a
discussion of some common misconceptions concerning black holes and general
relativity. In particular, the predicted radiance observed from Earth is found
to be orders of magnitude lower than what any instrument could detect, and the
PBH-BH merger signature would be completely overwhelmed by the background
Hawking signature from free PBHs.
