@DionIf you add two blank lines, a space, and two more blank lines it's a way to hack more spacing.
But that's not the point of the question, I realize. Believe it or not, it's not a request very many (if any) people have brought up before. A what-you-see-is-what-you-get editor is a pretty difficult technical challenge—even parsing BBCode normally is far less than trivial. But to answer your question, it's now something on my radar, but not something I'd expect to see working overnight.