The links are simply filtering threads based on what the seller tags.
In the Benedetto’s thread your shared, he did not tag “ca” but tagged “ca-socal” and “ca-norcal”. So his thread would not show up under Topics tagged marketplace & CA.
The best thing for Benedetto to do is to tag all three: “ca”, “ca-socal”, and “ca-norcal” for maximum visibility. There are historic reasons why the tags are set up the way they are. I do see it can be confusing…