I used to train SD and the basic stance they taught when we first started sparring was the right foot forward stance with your weight equally distributed among both feet so you can move in either direction quickly.
I've seen people fight with more weight on their front foot, like a 60/40 and to be honest... as soon as I see that I start plotting
Someone made a reference to that being similar to and older boxing stance and that would make sense... they don't have to worry about kicks. Its harder to check a leg kick from a 60/40 stance so you would probably end up taking some punishment. I know they did not train leg kicks in the SD school I attended so maybe that explains why some people might have adopted that stance. You're still vulnerable to sweeps though.