Markdown wierdness?

Some wierd stuff is happening with markdown. I have two different versions running in two different blogs. One is the version which ships with WP 1.2 and the other one is version1.0 by Micheal F. There are several things don’t work according to the documentation I’ve read here:
http://daringfireball.net/projects/markdown/syntax
let’s start with the first one. it says I should be able to create a <hr> by typing a line on its own like this
*** or * * * or — or – – – or ___ or _ _ _
this however generates html like this:
*
which I can understand, it is taking the * as emphasis.
Am I looking at the right documentation? Should I be able to generate an hr with the above code?
thanks.