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).
I was about to open a topic about this when I found this one, so I’m leaving a reply here.
I think it would make sense to have notifications for when a topic is open/closed if I’m tracking/watching it. If this is perhaps too “noisy”, then at least a notification to the topic author would be appropriate. It seems reasonable that, as a topic author, to know that a topic had been closed.
To be clear, my suggestion is not the part about having a custom text when closing a topic — that can be done with a post on the topic —, but rather about the lack of notifications for the close&open topic actions.
Sure, one can visit the topic to see it was closed, but if one visits it only if there’s replies, and there’s none because it was closed, it may take a while to find out why there’s no replies, depending on active it usually was.