Re: A quieter clutch cover plate
won't hurt anything. i think the reason there's even a gasket there in the first place is to keep the bolts from rattling out.
there's nothing in there that's gonna leak out, and unless you submerge your bike, nothing's gonna get in, so a thick rubber gasket should be fine.
i use Plasti-Dip spray paint on the inside of my cover. works as good as any rubber insulator.