With respect: "turn it off" isn't a fix.
I notice the main WYSIWYG thread (aka "Wish List") was "turned off" 11 months ago.
Excuse me, but when I go to blogger.com *Gack Ptui* I get Visual and Code. When I go to LJ (Are we gonna have to pledge allegiance to Putin?) I get a totally awesome WYSIWYG and a righteous source editor. Heck, I get a usable source editor when I add comments at ITtoolbox. But for some reason I don't get to use an honest source editor in WP.
To tell the truth I'd be happy to hear that this is a new problem. I was massively gob-smacked with the notion that folk have been putting up with this behaviour for years.
So ... I repeat: "turn it off" might be a sort of work-around, but it isn't a fix, because the "Source" editor imposes its own set of rules.
FWIW: I'm doing a survey of other editors (Xinha? I've never liked TinyMCE; I'm really angry at it right now; as I see more of the alternatives I like it even less. What's this I hear about it truncating long posts? *shudder*) When I have something like a short list I'll make a page at codex wiki.