  We analyze a well-known experimental work [J. Crossno et al., Science 351,
1058 (2016)] which reported on the failure of the Wiedemann-Franz law in
graphene at $T\sim 10$-$100\,\mathrm{K}$, attributing this failure to the
non-Fermi liquid nature of the Dirac fluid associated with undoped intrinsic
graphene. In spite of serious theoretical efforts, the reported observations
remain unexplained. Our detailed quantitative analysis based on Fermi liquid
considerations, which apply to extrinsic doped graphene, establishes that one
possible explanation for the reported observations is the opening of a gap at
the Dirac point, induced perhaps by the boron nitride substrate. We suggest
that more experiments are necessary to resolve the issue, and we believe that
the experiment may not actually have anything to do with Dirac fluid
hydrodynamics, but relates to finite-temperature low-density bipolar diffusive
transport by electrons and holes in the presence of short- and long-range
disorder, and phonons.
