I do confirm the bug with non-logged-in users. Unfortunately still trying to get a new laptop setup so I don't have access to any of my mod source files right now. Will look into it in a few days when I'm back online.
EDIT-
You could try editing the threadpassword.php file.
Change this line near the top:
From:
PHP Code:
define('CSRF_PROTECTION', true);
to:
PHP Code:
define('CSRF_PROTECTION', false);