MC cartridges and metal platters


I have read you should not use a MC cartridge with a turntable which has a metal platter, and Music Hall strongly recommends not to do so, at least on their Music Hall 2.2. However, every single HIFI dealer I have talked to disagrees and state they have done this countless times without problems. What is the truth?. 
boofer
Thanks again, Viridian; looks like my restored TD 150 and 160 Super pass the  nonpermeability test, and I can continue interchanging my 4 LOMC cartridges between them.   

czarivey: I looked up  QRK   turntables, found it quite interesting. Thanks for your input.
Post removed 
Remove your MC cartridge and place it on the side of the platter. If it sticks, don't use it. Send it to me.
What about Thorens zinc alloy composition platters, Viridian?Needless to say, I've forgotten my college chemistry.
Post removed