Patch for fixing the feeds:

<note> this is a test </note>

finally, I managed to repair the feed plugin. Actually, [NiKO] in the channel #dokuwiki in Freenode pointed me to the right patch:

=== modified file 'lib/plugins/blog/inc/feed.php'
--- lib/plugins/blog/inc/feed.php
+++ lib/plugins/blog/inc/feed.php
@@ -160,6 +160,7 @@
     '!<h1>(.*?)</h1>!s'                       => '', // remove title
     '#<!-- SECTION \[(\d*-\d*)\] -->#e'       => '', // remove section edit buttons
     '!<div id="blog__tags">.*?(</div>)!s'     => '', // remove category tags
+    '!<div class="blog_tags">.*?(</div>)!s'     => '', // remove category tags
  // '!</(p|h\d)>!s'                           => "\n\n",  // end of paragraphs
  // '!<li.*>!s'                               => '* ', // list items
  // '!<(br.*|/li|/ul|/ol|/tr|/th|/table)>!s'  => "\n" // line breaks

There seems to be a bug in the template, which outputs some other <div> block. hmrpf