The "here are you" node is not displayed, because of the Hierarchical's ItemTemplate.
If you remove it, you are able to create nested RadTreeViewItems as more as you wish.
The reason for this is that you are setting the ItemTempalte to have only one nested RadTreeViewItem.
You can check the attached project for demonstration of styling the same way all the RadTreeViewItems.
The main purpose for using HierarchicalDataTemplate is to apply different style for the different levels of the RadTreeView, but you should provide additional HierarchicalDataTemplatefor every nested level.