So, go on a wikia with badges enabled, let's check a badge, for example the Just the Beginning badge. You can see Awarded for making 5 edits on articles! This badge has been earned by X people.. But if you're an user who wants to know who got that badge on the wikia, then let's make it much easier for you.
So, now it looks like "Awarded for making 5 edits on articles! This badge has been earned by X people. Looks the same, but see that link over there? If this JS extension is enabled, there'd be a link showing ALL users who got that badge (remember: the Special:Usershavingcollectedthisbadge (which is also in serious need of renaming) works the same way as Special:Whatlinkshere does, if there are too much (i.e. over 100) people having earned the badge, there will be a "previous 100" and "next 100" thingy!)