They are not reserved characters. They only express a special format when used in that way : a space on its left, and a character stuck to its right AND somewhere down the road : its twin with a character stuck to its left and a space on its right. I built an editor doing just that more than two decades ago, and it works fine.

So *this* and /that/ express formatting, but not 4 * 5 nor 4*5 nor 4/5 nor m/s.