"Restore all default settings" in Special:Preferences should be a button, just like "Save" and "Undo changes". The text link looks odd at the moment.
Version: 1.21.x
Severity: minor
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=67338
https://bugzilla.wikimedia.org/show_bug.cgi?id=68689