It doesn't change between on and off, the button remains always the same (I' talking about the button that toggles the WYSIWYG state of the editor).
Also, it seems (but in that case it may just be my browser, I have to double check with another one) that when toggling from WYSIWYG to normal it adds an empty line at the beginning of the text.
If we toggled it "off" how would your return? ... toggle it to a different icon maybe :-\
Not sure on the line, would not surprise me, lines seem to appear and disappear when toggling back and forth.
Misunderstanding: I just mean that when in WYZZY mode the button doesn't have the green-ish background. :P
Oh that, yeah :-[