Speaking of weird, I've recently messed around a bit with d19, which was my first distribution of DF without Mayday's modifications. I've long ago read that being able to green- or red-light all types of stone wasn't supposed to be possible in vanilla, but here I'm doing just that in d19. Has this feature been included recently, or am I missing something?
It's not been included, I'm positive. I download and ran d19 (I use d16) and started up a fortress, and only the normal economic stones were available in the economic stones list. I also checked the raws and there was no CAT_MOUTH body part, so the cat-mouth glitch hasn't been fixed either. This matches the thread, which suggests that there have been no gameplay changes, though I wasn't sure fixing the cat-mouth glitch would count as a gameplay change exactly.
Are you sure you unzipped to a seperate folder? I haven't used Mayday's version, but if it installed a shortcut or something you shouldn't use that anymore. That's all I can think of.
Edit: I only tried the windows version, in case that matters.