The purpose of this comment is to correct mistaken assumptions and claims made in the paper “Stochastic feedback, nonlinear families of Markov processes, and nonlinear Fokker–Planck equations” by T. D. Frank [T.D. Frank, Stochastic feedback, non-linear families of Markov processes, and...

A self-consistent and universal description of friction and diffusion for Brownian particles (grains) in different systems, such as gases with Boltzmann collisions, dusty plasmas with ion absorption by grains, and for active particles (e.g., cells in biological systems), is suggested on the...