Well we did correct that at a point, but WordPress went full derp in 4.0 and removed functionality we (and other theme developers) were using to limit the editor’s width to the same width as you configured the theme to.
The only solution now is to remove the limiting entirely and let the editor go fullscreen, without any indication as to how your content will actually align on the frontend.
Please read the FAQs: Mantra • Nirvana • Parabola • Tempera
Tutorials: custom menus • translating theme • installing theme • category page with intro • disabling comments Wordpress: child themes • categories/posts
Tutorials: custom menus • translating theme • installing theme • category page with intro • disabling comments Wordpress: child themes • categories/posts