12TA it does not seem to show the GROUP that the current user belongs to
You are right! I get two lines of output, one for each group. So the introduction text should better be like this:
The following groups have privileges for the current page: ~~ACLINFO~~
Let me think about this!
Update: Try to integrate following two lines of code into the main.php of your template at:
/dokuwiki/lib/tpl/yourtemplate/main.php in some suitable place:
echo '<div>The current user belongs to following group: ' . $INFO['userinfo']['grps'] . '</div>';
This code could be easily expanded to loop over all groups the user belongs to, if it were more than one.