Some of the feeds that I subscribe to occasionally have video in them like YouTube. Does that mean that the feed never validates in these?
Most desktop feed readers cannot display Flash content, including embedded videos from sites like YouTube, and would basically display a blank area instead of the video, leaving the subscriber to wonder what you're referring to when you say "check out this video".
Since there's really no good way to support all feed readers and keep the valid according to today's standards, Viper chose to display the full URL, rather than the embedded video, when viewing the feed.
at the moment the feed (when using [Viper's Video Quicktags]) lists the link to the video provider rather than solely to the blog post with the video in.
This is a function of the plugin to provide some way of saying "this would be here". The link to your blog post should be handled by WordPress within the
<link> field of your RSS feed and the
<id> field of your Atom feed. Any standards-supporting feed reader should display this link along with the title of the post, either as part of one link or adjacent to it.