I believe the consesus is that the platinum plugs CAN leave platinum deposits in the engine which isn't good for it. I don't know if that means it will put platinum deposits in, but it can do it if the conditions for it to happen are met.
I also think essentially that the copper plugs do just as good of a job as the platinum ones.
I'm not a tech, but I'm more than willing to follow the advice of my fellow members here.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.