I'm looking at the renderers for the file-picker and manager and something has confused me.
In files/renderer.php there is the HTML for most of the pop-ups that you navigate when uploading and managing files in the file-picker. In this file's HTML most, but not all, of the class names have {!} inserted before them, e.g.:
<div class="{!}fp-toolbar">
Immediately after the string is initialized with multiple of these "{!}" a regexp is used to strip them back out again.
return preg_replace('/\{\!\}/', '', $rv);
https://github.com/moodle/moodle/blob/master/files/renderer.php#L262
Just one would look like a mistake but 10 or so of them makes me think I'm missing something clever that's happening.