Simulated by switching off JS in Chrome.
|SET: Set user's editor to wikitext if the browser doesn't do JS||mediawiki/extensions/VisualEditor||master||+28 -11|
So we give this blank page because of concerns that by loading VE on the top of action=edit, we'd be sending the revision text twice. The server expects the client to load VE, which the client-side code should handle - but it might not actually run that code.
Maybe we should provide some sort of link like 'Click here if the visual editor does not appear to force use of the wikitext editor', which sets their cookie/pref to wikitext and (if logged in) preference to always prefer wikitext, and loads the wikitext editor?