Yeah, if I'm interpreting your words correctly, this would be like turning

  p {b This} {b text is} {b bolded} this isn't

into

  p {b This text is bolded} this isn't

But then the issue is as follows:

In Polymath, I'm planning on allowing basically arbitrary CSS styling by parent, id, class, etc. So if the user later wants to do something like put a rounded box around each span of bolded text, those two, while initially looking identical in WYSIWYG, end up completely different.