In this work, several philosophical points with respect to the momentum equation in a porous medium are analyzed. The authors show that several erroneous/irrelevant issues were put forward in previous work. A porous medium/clear fluid interface is best dealt with by the Brinkman-Forchheimer-extended Darcy formulation and the continuity of velocities and stresses at the interface. The effect of porosity variation is not required for a high-porosity medium but should be considered for a dense porous medium.