Here it is for 2.2.8 in the forumdisplay.php file. The usergroupIDs are those used in the text file attached in the first and 48th post:
Find (line # 698 in the original source file)
Code:
if ((!$forumuser['invisible'] or $bbuserinfo['usergroupid'] == 6) and $bbuserinfo['userid'] != $forumuser['userid']) {
Replace with
Code:
if ((!$forumuser['invisible'] or $bbuserinfo['usergroupid'] == 6 or $bbuserinfo['usergroupid'] == 7) and $bbuserinfo['userid'] != $forumuser['userid']) {