
It appears that, for whatever reason, 3D floors render visible through adjacent reflective surfaces. This is using the OpenGL renderer on the x64 build from April 29th. Attached to this post is a simple .wad using the same settings without all the KL2 stuff.
EDIT: I thought it might have been some sort of issue with my configuration, but removing reflectivity from both the 3D floor's surfaces and the floor of the actual sector did nothing to change this.