My tool doesnt use -quant n
maps.mk will use -quant 4 btw
It would be nice if a mapper could clarify this option
I'm not sure if any of us know technically what it does, but in the end it produces much sharper shadow lines. If you look at the shadows closely, you will see that an angled shadow line comes out in small squares (like pixels). Lower quant reduces the size of these boxes to produce cleaner shadow lines. It's not the difference between "blurry" and sharp, but about straight or broken into little squares.
Mattn was playing with the default -quant setting recently, but I don't know where he left it. Small quant values (such as 2) resulted in map compiling errors for some maps (max lightmap). Quant 2 is tons better than 3 and in my opinion our goal should be to support it, but I'm not sure anyone knows a good way to get there. I was told increasing lightmap size is not a good idea.