Here is my RSS Feed: http://sck-mobile.com/community/index.php?forums/-/index.rss.
The result of my RSS Feed, was this: http://validator.w3.org/feed/check....le.com/community/index.php?forums/-/index.rss
Now I know that it has been ruled that the XenForo RSS Feed has NO Bugs, but there IS something 'buggy' about it. Maybe this thread can be posted into the 'Requests' area, if nothing can be done about this? Alot of great content 'should' be able to be passed through RSS Feeds IMO.