I was just wondering if the fabric would facilitate leakage via air passing through the very small gaps between the rubber mounting section of the subwoofer (part you screw into the box) and the wood. Because my last setup was just sub on wood (no porous carpet in-between) and that was about as sealed as I could get, so I was worried the fabric would cause said seal to have a slight but sub optimal leakage. I thought it was a pretty good question, I'm usually the first to say something like "are you serious" when someone asks a seriously dumb question but it's a shame that someone with such a strong site-presence reacted in such a way in this case. (not referring to you, whoever I quoted)
edit
by flat I meant bare wood. because carpet is not perfectly flat it has valleys/grooves. They're small but so are air molecules. Hope that clears up any confusion.