Comment on: “Hyperfine structure measurements of Co I and Co II with Fourier transform spectroscopy” by Fu et al. [JQSRT 2021, 107590]

•Fu et al. (2021) published a hyperfine structure analysis of 61 Co II energy levels without reference to the existing extensive study in the literature of Ding and Pickering (2020).•43 Co II magnetic hyperfine interaction constants published by Fu et al. were in agreement within uncertainties with those published previously by Ding and Pickering.•Large discrepancies were found in 17 Co II magnetic hyperfine interaction constants of Fu et al. The new A constant of 3d64s2 a5D4 reported by Fu et al. is found to agree with observations by Ding & Pickering.•Fu et al. had analysed experimentally unclassified lines at Ritz wavenumbers 25453.968 cm−1 and 25149.948 cm−1 to attempt to determine the magnetic hyperfine structure constants of energy levels 3d7(2G)4s a3G5 and 3d7(2P)4s c3P2 respectively. This caused most of the discrepancies.