What a pity that the same doesn't go for em, en and thin spaces
(which aren't usually present in any fonts). If you are going to use
em dashes with a thin space either side - which is how we use them -
in most applications you have to change the point size or horizontal
scaling of the word space to achieve a thin space. This plays merry
hell if you want to globally change the formatting of the text.
Why I use TeX :-)