I have exactly the same question! Did you find any way to hide it?
No I haven't been able to yet.
I appreciate the help, but that's not going to work for what we need.
We would need something dynamic because if say 5 articles are published today for Categories that we have hidden, I would have to go in as an admin and make sure to show those Categories. It would be better off just showing them all to begin with.
It's not a huge problem though, it would just be nice to have a more dynamic Self Service view.
Now I remember... when I had that issue I ended giving up
Just an Idea.
Create a new flag im FRS_Knowledge and call it "FLG_VissibleForSelfService". Change the security settings for the role hat only articles with this flag will be shown.
Create a business rule which changes the flag to true as soon as an article for a category was created. I haven't tested it but I think this could work.