Without the description field in the RSS feed (you can see the current feed here) it is impossible to follow the forum using any of the popular RSS Readers. Sure the post titles will show up, but no content is provided. RSS Readers are very useful, not only because they notify you of a new content, but also because they format posts to be easy to read on tablets and mobile. It is not a limitation of the forum software (XenForo), but maybe a configuration setting. You can see it working properly on XenForo: http://xenforo.com/community/forums/-/index.rss