Fix-ups to comments and User interface usages

* Use isRegistered() from the more narrow UserIdentity interface.
* More specific type hints.
* Remove comments that literally repeat the code.

Change-Id: Icd0eaf8236be41b258efcf81d581540d2448e9e3

scripts/compile-font-repo.php

@@ -1,6 +1,5 @@
 <?php
 /**
- *
  * @author Niklas Laxström
  * @license GPL-2.0-or-later
  * @file

scripts/generate-font-test-page.php

@@ -1,6 +1,5 @@
 <?php
 /**
- *
  * @author Niklas Laxström
  * @license GPL-2.0-or-later
  * @file