Details

I explained everything in my following post:
http://expressionengine.com/forums/viewthread/68022

Since it is a bug in the current version of the Discussion Forum module, you can check the HTML source of the page above, to see the effect.

Basically if you have a quote with paragraphs within another quote, the page source will not validate. The issue is that the <blockquote> and tags (used for to display the quotes) get all messed up inside one another. Some tags loose their opening tags, some don’t have a closing tag.

This can cause display problems on a site.