By default, the node tag can be used without any of the parameters that add content (the parameters without the [no content] comment in their description title.) In that case, the content of the node is inserted as if content had been specified.
However, since version 6-1.1, the theme of the default parameter can be overloaded. This means you can change the default by writing a function to overload the default.
CSS Class: div.insert-node-content
Theme: InsertNode_default