Contrary to what has been posted earlier, the X wasnt simply put in hXc because it looked cool. It originated back in the punk scene in New York back in the '80's.
Originally, NYHC was written on a white shirt with the N to the left side of the X, the Y to the right. The H was at the top portion and the C at the bottom. Looking similar to this:
This is back in the day, before the labels of "emo" or "scene" or some other moniker the sheep can come up with.
This was Punk, it was Anarchy, it was Hardcore. Not the sad perversion that it has become today.
"The Mob" put NY hXc on the map.