So I eventually realized my old Pelikan M400 had my least smooth nib, by far, while I remember it used to be smooth... It was more like dragging a rough piece of metal on paper, and Clairefontaine at that, with clear resistance and a sound reminiscent of nails on a blackboard, while even my cheap Mujis and Lamys glide... I remembered I had some micro mesh or whatever it's called, can't remember what I got it for, and decided to give it a go... That sort of idea usually ends in tears for me, but this time the nib clearly improved and is smooth again. I didn't use the micro mesh much, just did some "8" figures. So the question is: why did it get "draggy" over time? It's not exactly that the nib felt rougher, but it would sort of cling on to paper. What is it that the mesh removes?