The idea of the Visual Editor is to provide visual feedback to editors about the changes they're making. However, for displaytitle modifications (via ≡ → Advanced settings → Display title) there is no feedback at all in VE. The page title is a visual element, yet the VE always shows the original title, there is no error message about disallowed modifications, and on top of that it reports "no changes" when reviewing changes visually.

So clearly this functionality is not ready and should be disabled until at least it does something "visual".