White space added after each removed tag

When the module removes a tag, it adds a white space in it's place.
Example:
<a href="example.com">This is a link</a>.
will turn into
This is a link .
(notice the space before the dot)

It seems that the source of this bug is this preg_replace:

            // Strip tags
            $output = strip_tags(str_replace('<', ' <', $output));

By the way, why do you use strip_tags() instead of Drupal's filter_xss() function?