When does adding a tag to a topic cause the topic to be bumped?

[codinghorror (Jeff Atwood)]

@RobMeade

Quite frequently, performing a moderator role, I will edit a post and add a specific tag to it. I have noticed that when I do this, this action is considered to be “activity” and as such the topic is listed as being the latest etc, bumped if you will.

This will only happen if the first post is the only post in the topic.

Edits to the last post in the topic bump the topic.

When a topic has only one post, you are editing the last post (and the first post).