Hi. In the latest pre-release, I've found that carpets don't cover lighting. I've specifically checked this with glowstone and beacons. This defeats the idea of having single block floors, since even if you cover the upstairs floor with an alternative surface, like a carpet, light would still come through through the lower floor's ceiling. Logically, carpets should at least cut the light level of the light source by about half, if not obscure it completely for usability reasons.