RSS feeds are based on the view permissions for pages and spaces. RSS is an extension of normal page viewing functionality, so if you can view a page, you can receive an RSS feed for it. The only way to remove an RSS feed is to prevent all access to a page for that user, so that no content will be delivered.  However, it is possible to remove all RSS feeds from Confluence just not individual feeds.  For more details on removing all RSS feeds from Confluence please see (Archived) How do I disable RSS feeds?