I have been using the michelf markdown transformer for a long time now, and I would like to use it in comment system. There is no way to tell the parser to add attributes to a link (like the rel="nofollow", but it is faily easy to extend the class and override the methods which does the link parsing.
You will need to override the following two methods:
I added the following filter to an old php framework, and called it markdownNoFollow. This class will add the rel="nofollow" attribute to links.
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