Why the insistence on a WYSIWYG editor? The best method of producing documents that I have ever used is LaTeX and it has no decent WYSIWYG interface (LyX does not provide the full power of TeX).
I don't think this particular editor, or any other WYSIWYG editors I'm aware of, are really targeted at the use case you're referring to.
Most of us deploying WYSIWYG editors are doing so in applications designed for non-technical users, where text markup is required but no technical knowledge on the users' part can be assumed.
Up until this point we’ve been using either plain text, manual HTML, or Textile formatting. Depending on who you are it’s either fine or annoying.
Regardless of how awesome LaTeX may be, a tiny fraction of people even know what it is. You shouldn't have to learn LaTeX to use 37signal's products...
