We argue that the theories of Volokitin and Persson [New J. Phys. 2014 = arXiv:1405.2525], of Dedkov and Kyasov [J. Phys.: Condens. Matter 2008], and Pieplow and Henkel [New J. Phys. 2013] agree on the electromagnetic force on a small, polarizable particle that is moving parallel to a planar, macroscopic body, as far as the contribution of evanescent waves is concerned. The apparent differences are discussed in detail and explained by choices of units and integral transformations. We point out in particular the role of Lorentz contraction in the procedure used by Volokitin and Persson, where a macroscopic body is `diluted' to get the force on a small particle. Differences that appear in the contribution of propagating photons are briefly mentioned.