When someone posts in a topic that I am subscribed to and have bookmarked, and he quotes me in the post, I get two emails (for the bookmark and the subscription) and three notifications (the former two plus for being quoted).

How to reproduce:
I configured my notification settings to receive email for both bookmarked and subscribed topics, but only get an on-site notification for being quoted.

What goes wrong in the code?
The notifications are added in the order quote, bookmark, subscription (functions_posting.php).

1. Because I disabled the email method for quote notifications, my username is added to the ignore_users array with only the empty string method disabled.
2. Now when the bookmark notification is added, the email method is still allowed and I get an email and the second notification.
3. Because phpbb_notification_manager->add_notifications() uses array addition (with the + sign) to update $notified_users, the initial ignore value of only the empty string is kept with my username, and the subscription notification is still allowed on the email method, resulting in the second email and third notification.