  A recent paper studies a modification of Einstein-aether theory in which the
aether vector is restricted, at the level of the action, to be the gradient of
a scalar. In this comment we note that this scalar version of Einstein-aether
theory is equivalent to the projectable version of the IR limit of Ho\v{r}ava
gravity when the potential for the scalar is constant. This provides a
generally covariant formulation for projectable Ho\v{r}ava gravity.
