As observed on https://qa.moodle.net/mod/forum/discuss.php?d=2 (log in as a teacher), the ratings help pop-up opens a window containing the header and footer of the site and a dropdown menu which doesn't do anything. The window has the confusing title of 'Scales'.
The problem occurs in both Boost and Clean.
(Sorry for not being able to find a previous issue relating to this problem. I think it has existed in several versions of Moodle.)