The “Auto-close topic after:” category setting is set to 6 months.
The “Don’t close until the last post in the topic is at least this old.” category setting is enabled.
And to eliminate it from consideration as a possible factor, I’ll also mention that the “Number of open topics to automatically bump daily” category setting is set to 0.
It is fair. It is complaints from users about the auto-close bumps that motivated me to make this request.
Although less impactful due to occurring less frequently, it also doesn’t make sense to bump a topic when it is archived, and I also don’t think it makes sense to bump a topic just because it was unpinned. This is why I generalized my request instead of making it specifically about auto-close.