Sure, that's understandable. There's a reason I prefer to write Markdown when I can and not XML, LaTeX or HTML. I think it's slightly odd that line-breaking algorithms would all do the wrong thing on "« " and " »". It seems like something that should be easy to automate, even if only in French… But anyway, my point all along has been about HTML5, not personal preferences.
Btw, what do you use to protect against accidental "« " over "«*"? (Assuming those came out correctly.) [Edit: I just noticed that this forum seems to have changed all of my non-breaking spaces into asterisks.)
PS In LibreOffice I just noticed that non-breaking spaces come with a gray background. Not bad. I wonder if I can make Geany do something like that, because obviously nobody would actually prefer an ugly nbsp… it's just that sometimes ugly beats invisible.