If you want to check if user belong to group use in_array i don't know what look like this option comma_delimited_groups_custom_mod_option
but it should be user group callback and if it's you can check in template like this
HTML:
<xf:if is="in_array($xf.visitor.user_group_id, $xf.options.comma_delimited_groups_custom_mod_option)">
<!-- some code here -->
</xf:if>