This will do the same thing, only much better.

Fixed:

$cats = get_the_category();
foreach ($cats as $cat) {
$catlinks[] = '<a href="'
.get_category_rss_link(false,$cat->cat_ID,$cat->category_nicename)
.'">'.$cat->cat_name.'</a>';
}
echo implode(' and ',
array(implode(', ', array_slice($catlinks,0,-1)),
$catlinks[count($catlinks) -1]));


example.com/authorname/feed/

You can read more in Blog Herald Feeds and Customizing Your WordPress Blog Feeds and Understanding, Using and Customizing WordPress Blog Feeds.