I’m afraid this isn’t really possible in Scrivener. I’m the Mac developer, and I know for a fact that this sort of thing isn’t possible using the Mac text engine (hiding text in general isn’t possible). I’m not sure about the Windows text engine our Windows developers use, but I’m fairly sure that has similar problems. And even if it didn’t, the underlying format we use for saving the text files (RTF) doesn’t have this capability, so it would mean extending the format.
I do agree that it’s a pretty nifty feature, but I’m sorry to say that it is out of scope, at least for now.
Thanks and all the best,
Keith