  In the recent study of the metal-insulator transition (MIT) in the disordered
crystalline solid SrNbO$_{3-x}$N$_x$ by Daichi Oka et al. [Commun. Phys. 4, 269
(2021)], the data evaluation relies on the Al'tshuler-Aronov theory of the
interference of electron-electron interaction and elastic impurity scattering
of electrons. The present comment shows that this evaluation approach is
inappropriate. For that aim, we reconsider data for the samples with $x = 0.96$
and $x = 1.02$ from three different perspectives: (i) analysis of the
logarithmic temperature derivative of the conductivity, (ii) study of the
deviations of the measured conductivity data from the Al'tshuler-Aronov
approximation of the temperature dependence, and (iii) comparison of the
measured temperature data with the values obtained treating the sample as
secondary thermometer in terms of that approximation.
  This way, for the sample with $x = 0.96$, classified as metallic by Daichi
Oka et al., qualitative contradictions between the measurements and the
zero-temperature extrapolation according to the Al'tshuler-Aronov theory are
uncovered. Thus, this sample very likely exhibits activated instead of metallic
conduction. In consequence, our findings question the continuity of the MIT
resulting from the highly cited scaling theory of localization.
