Ok, although I think the name is terrible (try using a search engine to find any information about “Discount”), the project seems pretty cool. Though I have my gripes with Markdown it is well suited for a number of applications:

• discount (markdown in C) announcement

I don’t even recall what I was looking for but I came across Maruku which is a library that implements the Markdown syntax, the PHP Markdown Extra syntax, and its own meta-data syntax. It should fix problems with underscores in links. It seems like the Markdown with SmartyPants module for Drupal also uses PHP Markdown Extra in its version for Drupal 6.0. That should be nice should I upgrade at some point. But I will start using Maruku on my Rails apps now and see what happens.

I really like Markdown but I've grown tired of a couple of it's problems. Mostly I get annoyed with using underscores for emphasis/italics. Underscores come up in web addresses and in text describing code and computer operations all the time and with Markdown I often find myself having italics where I wouldn't want it. Now it's possible that there are some bugs in the parser but it's also possible that the syntax is correct. I think if I had to make a proposal for a better system would I would use much of Markdown but have the following syntactical additions/changes:
**bold** __underline__ ++ins++ --del-- //italics//