  Laffont et al. [Science 363, 54-57 (2019)] report an upstream current in the
nu=2/3 quantum Hall regime, which, they claim, might be due to a
counter-propagating charge mode. We show that this observation can also be
explained by the expected upstream neutral mode, without the need for an
upstream charge mode. Our results agree with the observed data and explain why
the upstream current is observed only in the unpolarized nu=2/3 regime.
