Well actually one arguement against that is that the point TheRogue1000 was making. That people might use mac at work & pc at home or vice versa. That's one of the reasons they zip mac files instead of a mac compression. (Or alternatively to be able to safely pass thru a window's environment - since mac files have xtra data that windows os doesn't understand & might do something damaging to. A difference of file systems.)

All the same it would be good to be able to identify the other file's origin operating environment.