I tend to agree with the responses you received from @cd318 and @squeak_king_77 . As examples, the widely used
Equipment Vibration Protectors (EVPs) are offered with either rubber or felt backing on the top or bottom - with no discussion about any change in sonics or performance. Also, Sound Anchor's Conecoaster spike support discs come with a felt-like material on the bottom and I was able to successfully slide my large speakers around on hardwood floors when I used those.
Of course, as usual, @millercarbon provided the most reasonable response!
Of course, as usual, @millercarbon provided the most reasonable response!