Based on our studies, GFN2/D4 appears best parameterized for species with polarizabilities less than 50 Å3 . In its current implementation GFN2/D4 does not compare favorably to DFT-computed polarizabilities in highly polarizable oligomers. We note that in addition to limiting GFN2's usefulness in its present form as a polarizability method for larger and/or conjugated systems, this raises important concerns about the D4 model's accuracy for similar systems, since the methods share the additive polarizability model.