It is impossible to build a clear and convincing conclusion about which density functional should be used dealing with a single compound. There is a substantial number of hybrid density functionals, which yield approximately the same results. As an example, in Figure the B3LYP spectra prediction is shown and in Figure some others are given. The experimental spectra of 3a-c shown in Figure have the typical shape for hydrazone form dominated mixture of o-hydroxyazo dyes, namely complicated spectral envelop around 500 nm. The absorbance of the azo form could be expected around 400-440 nm. In the spectra of 3a and 3c, there is a weak shoulder in this region that could be attributed to some amount of A as suggested by the calculations and the existing in the literature experimental results. In the case of 3b there is an additional blue shifted band at 444 nm, but the spectra of both tautomers have complicated signature, which makes the exact assignment in a single solvent unreliable. As seen from Figure and S3-5 there is no reliable theoretical prediction of the optical spectra taking the tautomerism into account. In all density functionals the spectral separation between A-and H-tautomers is negligible, i.e. the tendencies mentioned in the case of 3 are worsened by the additional substitution in the naphthyl ring. In the original paper, the authors do not give much details about the selection of TPSS as the best performing functional, but the result show clearly how it is unreliable to make general conclusions based on a small data set benchmarking or on only a single family of structurally similar compounds. And without to take the tautomerism into account.