  In a recent Letter, Guarnieri et al. [1] reported on the possibility of
generating steady-state coherence (SSC) in the energy basis of a two-level
system by the sole action of a single thermal bath also for weak system-bath
coupling and due to a composite form of this interaction. The results are based
on a time-local Bloch-Redfield master equation without secular approximation
and the associated set of Bloch equations, all derived in the Supplemental
Material (SM) of Ref. [1]. We comment that the results reported by the authors
present both technical flaws and conceptual limitations that substantially
impact some of their main conclusions. Our objections mainly concern (a)
technical errors in the calculation of SSC (Eqs.(2)-(4) in [1]) and (b)
negativity issues associated with the weak-coupling master equation employed by
the authors.
