in reply to (OT), who decides, who adds it?

In most cases, a node is considered by any monk, Friar or above.
Once there are sufficient votes for "edit", one of the editors will amend the node as mentioned in the consideration.

IIRC, the node in question had a large number of edit votes.

So, the answer is, everyone decides if a node is off-topic or not.

If the information in this post is inaccurate, or just plain wrong, don't just downvote - please post explaining what's wrong.
That way everyone learns.