What's your trick to document (in the UI?) variables overridden in settings.php? If you define variable overrides in settings.php, there is no visible change to the admin UI. It's easy when overtired (or just inexperienced) to overlook this when changing some config through the UI, and getting an unexpected result.

Have people come up with a trick to document settings.php overrides right in the related admin form? I guess I could write a form_alter every time I define a settings.php override, but is there an alternative clever that devs are using? (I'm using D7, BTW.)
You could implement a hook_help that displays a message on the page where you would set the variable. Would still need to do it manually per variable though.