Not italicising URLs with underscores

Hi,

I notice because of Markdown's underscore policy, urls with underscores get italicised bits.

For example, a wikipedia link of http://en.wikipedia.org/wiki/The_Taming_of_the_Shrew

would come out with 'Taming' in italics, although the underlying link will be ok. I noticed on groups.drupal.org this problem doesn't exist. How do you get over this?

My input filters are in this order:

HTML Corrector
HTML filter
googtube filter
URL filter
Markdown with SmartyPants

Thanks for any help.

Cheers