As the name immplies I would think it would be neat if there was an extention that allowed nodal categories. I like to be organized but there are somethings that I want only certain roles to be able to access and comment while at the same time the most logical place for them to be is as part of a sub category.
You are not the first one to ask it. There is at least one discussion per week created for this request. Someone who want it should start to work on it.