I seem to have solved it now.
Just in case anyone wants to know, I show the changed code here.
In extern.php line 442 I changed this code:
// Fetch $show topics
$query = array(
'SELECT' => 't.id, t.poster, t.subject, t.last_post, t.last_poster, p.message, p.hide_smilies, u.email_setting, u.email, p.poster_id, p.poster_email',
'FROM' => 'topics AS t',
'JOINS' => array(
array(
'INNER JOIN' => 'posts AS p',
'ON' => 'p.id=t.first_post_id'
),
to this:
// Fetch $show topics
$query = array(
'SELECT' => 't.id, t.poster, t.subject, t.last_post, t.last_poster, p.message, p.hide_smilies, u.email_setting, u.email, p.poster_id, p.poster_email, p.posted, p.id',
'FROM' => 'posts AS p',
'JOINS' => array(
array(
'INNER JOIN' => 'topics AS t',
'ON' => 't.id=p.topic_id'
),
And at line 480 I changed this code:
$item = array(
'id' => $cur_topic['id'],
'title' => $cur_topic['subject'],
'link' => forum_link($forum_url['topic_new_posts'], array($cur_topic['id'], sef_friendly($cur_topic['subject']))),
'description' => $cur_topic['message'],
'author' => array(
'name' => $cur_topic['last_poster']
),
'pubdate' => $cur_topic['last_post']
);
to this:
$item = array(
'id' => $cur_topic['id'],
'title' => $cur_topic['subject'],
sef_friendly($cur_topic['subject']))),
'link' => forum_link('viewtopic.php?pid=$1', array($cur_topic['id'])),
'description' => $cur_topic['message'],
'author' => array(
'name' => $cur_topic['last_poster']
),
'pubdate' => $cur_topic['posted']
);
Now I get all replies and not just the topic. Thanks for the hint for solving this.