Never seen it or heard of it. I've always used Luke warm water to clean my pens; just a few fills until the water runs clear, several good thermometer shakes and a drying over several days with the cap off and my pen is good to go. I've not had a severally gummed up pen, but I think this method would work, perhaps with a short soak of the nib and feed. I don't think the Diamine is watered down nail polish remover sans acetone, as even without the acetone it could contain chemicals injurious to the inner workings of a fountain pen. The Luke warm water method is entirely benign and won't harm your pen unless it's made of casein, a milk-based plastic, but this would be most unusual.