IMHO the confusion over having a discussions at the clearspace and at the sub-space is a configuration design issue.
Given that Jivesapce is covering the Jive product line, it's logical that it has it's own space and sub-spaces. It is a configuration choice to set-up a space to have discussions.
On the current set-up, I also don't understand the differentiation between the group of discussions at the top and leaf level - certainly in the context of feature discussions. See also New Feature: Sub-Space roll up under Parent-Spaces
One observation is that the discussion, documents or blogs tabs for that matter don't have any/their own descriptive text. The context is set entirely by the description of the space.