Categories... In the actual categories ?

I had an idea recently, inspired by a forum I used to visit a short time ago. Long story short, the posts were classified this way :

See ? It's in french sorry, but there is a first type of category, "Informations", and then the second levels of category, "Annonces jeu", "Annonces forum" and "Annonces communauté". And inside those, are the posts !

This would be really helpful, for us web designers ;)