Comment on: New limit on lorentz-invariance- and CPT-violating neutron spin interactions using a free-spin-precession 3He- 129Xe comagnetometer

In Ref. [1], the authors use a classical result for the magnetic field created by a uniform magnetization to analyze the effects of magnetic interactions between 3He and 129Xe nuclear spins. We point out that the classical result is not applicable for interaction between nuclear spins: the actual interaction is much weaker. This calls into question the results of their analysis setting limits on Lorentz invariance. We also point out that the Letter does not contain any discussion of systematic errors in the determination of Lorentz-violation coefficients.