IMO even without debris the clay will mar, it is the clay per se that causes it. At the ends of the glide where the hydrodynamic lubrication film breaks down the clay will hard contact the paint. At least thats how I treat it. That said, I also assume even microfiber will mar and swirl paint (it has!) until I try and find it unnoticeable.
Ended up selling my Berlina Black S2000 because my best microfiber would mar the paint, "aint [nobody] got time for that"!
Ended up selling my Berlina Black S2000 because my best microfiber would mar the paint, "aint [nobody] got time for that"!