Quick solution:
1. Open file /administrator/components/com_jcomments/admin.jcomments.html.php
2. Replace:
he.innerHTML = '<?php echo JText::_('A_RIGHTS_GROUP_DESC'); ?>'+' <span style="color: green">'+jc_usergroups[i]+'</span>';
with
he.innerHTML = '<?php echo addslashes(JText::_('A_RIGHTS_GROUP_DESC')); ?>'+' <span style="color: green">'+jc_usergroups[i]+'</span>';
Sorry... This is very stupid bug... It will be fixed in upcoming version.