The link to a text on Amazon in my answer here, http://music.stackexchange.com/a/9590/1344 , isn't turning into a 'rad'. Do I have to do something different? I thought they should be automatically replaced.
Shortlinks aren't converted.
If you use the full link, in this case http://www.amazon.com/dp/0486460436/ref=cm_sw_su_dp, it will be.