use a double-dash -- like these in the input -- to get a nice smooth typographic em-dash in your output, such as the .html. it's best to put spaces around your double-dashes, or else they can sometimes cause word-wrap problems.
don't use a single-dash - like this bad example - where you want an em-dash, or it will look _bad._ even http://medium.com and http://kottke.org make that mistake. it's rather embarrassing, eh?