Hi,
I use a content plugin to fix the output. The main tag component uses this plugin. The module does not. But you can add a template override for that module. It will call content plugins and the output will look as expected.
modules\mod_tags_similar\tmpl\default.php
<?php
/**
* @package Joomla.Site
* @subpackage mod_tags_similar
*
* @copyright Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
* @license GNU General Public License version 2 or later; see LICENSE.txt
*/
defined('_JEXEC') or die;
$dispatcher = JEventDispatcher::getInstance();
?>
<?php JLoader::register('TagsHelperRoute', JPATH_BASE . '/components/com_tags/helpers/route.php'); ?>
<div class="tagssimilar<?php echo $moduleclass_sfx; ?>">
<?php if ($list) : ?>
<ul>
<?php foreach ($list as $i => $item) : ?>
<?php $item->text=''; $dispatcher->trigger('onContentPrepare', array ('com_tags.tag', &$item, &$params)); ?>
<li>
<?php if (($item->type_alias === 'com_users.category') || ($item->type_alias === 'com_banners.category')) : ?>
<?php if (!empty($item->core_title)) :
echo htmlspecialchars($item->core_title, ENT_COMPAT, 'UTF-8');
endif; ?>
<?php else : ?>
<?php $item->route = new JHelperRoute; ?>
<a href="https://www.svenbluege.de/<?php echo JRoute::_(TagsHelperRoute::getItemRoute($item->content_item_id, $item->core_alias, $item->core_catid, $item->core_language, $item->type_alias, $item->router)); ?>">
<?php if (!empty($item->core_title)) :
echo htmlspecialchars($item->core_title, ENT_COMPAT, 'UTF-8');
endif; ?>
</a>
<?php endif; ?>
</li>
<?php endforeach; ?>
</ul>
<?php else : ?>
<span><?php echo JText::_('MOD_TAGS_SIMILAR_NO_MATCHING_TAGS'); ?></span>
<?php endif; ?>
</div>
Please don't change the original file. Place it in your templates override folder to avoid issue with updates in the future.