  A recent claim of possible superfluid behaviour of parahydrogen films
intercalated within a crystalline matrix of Na atoms is examined. Quantum Monte
Carlo simulations at finite temperature yield strong numerical evidence that
the system forms at low temperature a non-superfluid crystalline phase,
commensurate with the underlying impurity lattice. The physics of this system
is therefore qualitatively identical to that observed in similar settings,
extensively studied in precedence. Comparison of numerical results obtained
here, with those of the reference in which the prediction of superfluidity
(disproven here) was made, points to likely bias in the computational
methodology adopted therein.
