  A modified f(R) gravity model has been recently proposed in Phys. Rev. Lett.
102, 221101 (2009) [arXiv:0905.1941] whose cosmological behaviour is clearly
distinguishable from LCDM. Contrary to previous opinions which consider that
self-consistent f(R) gravity models distinct from LCDM are almost ruled out,
the authors claim that the proposed model is cosmologically viable. Here we
show that although the model satisfies some consistency conditions, precisely
because of its departure from LCDM behaviour, it does not satisfy local gravity
constraints and, in addition, the predicted matter power spectrum conflicts
with SDSS data.
