http://www.rssboard.org/rss-specification#ltguidgtSubelementOfLtitemgt
<item>
<title><?php print $item->getTitle() ?></title>
<link><?php print $item->getUrl() ?></link>
- <guid<?php if( $item->RSSIsPermalink ) print ' isPermaLink="true"' ?>><?php print $item->getUniqueId() ?></guid>
+ <guid<?php if( !$item->RSSIsPermalink ) print ' isPermaLink="false"' ?>><?php print $item->getUniqueId() ?></guid>
<description><?php print $item->getDescription() ?></description>
<?php if( $item->getDate() ) { ?><pubDate><?php print $this->formatTime( $item->getDate() ) ?></pubDate><?php } ?>
<?php if( $item->getAuthor() ) { ?><dc:creator><?php print $item->getAuthor() ?></dc:creator><?php }?>