Hi, I found that admin operations such as listing/unlisting a topic or changing its category are considered as a new reply to the topic. Then this topic would appear under the Latest tab even though there are no REAL replies to the discussion.
I see what you mean, don’t forget though, that when closing or unlisitng a topic, mods and staff have the ability to add text in those notifications. That’s why they count as a reply. It also indicated the last person who replied in that topic.