Looking at the code, the hooks are DOM listeners that intercept the click to do ...

dschoon on April 30, 2010 | parent | context | favorite | on: Posterous silently changes all external links to a...

Looking at the code, the hooks are DOM listeners that intercept the click to do the redirect. They don't modify the anchor tag, so there's no reason anyone should see them on mouseover or right-click-copy.