Feed Viewer identifies itself by this string:
User-Agent: FeedViewer/1.0 (+http://www.feedviewer.net/webmasters; license agreement: http://www.feedviewer.net/license). You can exclude Feed Viewer from browsing your web by denying its requests recognized by this string.
If you insert the code
<meta name="robots" content="noindex"> to the page, or serve it with
X-Robots-Tag: noindex header, Feed Viewer will not display it.
By disalowing syndication feed in
robots.txt file, Feed Viewer will not show it in search results.