I just noticed that when a topic is closed, no notification is sent.
For example here (Cursor misalignment in the categories box (Firefox)) happened to see that the bug was fixed some days ago but I only saw this today, by looking at the list of suggested topics.
I think it’s a useful feature in forums frequented by many users and it helps to keep track of all the topics a user can have opened days or months before, if it is closed for a specific reason with a text added by one of the admins/mods (this does not trigger notifications for the topics set to be closed by @system).