Unfortunately XHTML5 doesn't exist and if you try to force the issue, you have to re-declare all of the non-numeric HTML entities in your own DTD (I abandoned the idea here). I'd love to use XHTML, its just not viable anymore.
As for generating all HTML, that's simply not possible given the current state (of open-source at least) WYSIWYG HTML editors.
I stopped using entities once we had UTF-8. I suppose there’s a case for the occasional < > but beyond that, I have no problem typing “‘—’” or üçě when I need to.
As for generating all HTML, that's simply not possible given the current state (of open-source at least) WYSIWYG HTML editors.