I should probably have filed this as a bug report. The issue is that the commit message populated by arcanist looks different, in a surprising way, to the way the Summary information is displayed on the Differential page.

To be clear, I started with the Side-by-Side view, which I guess is the default. And I can't return directly to the side-by-side view with the original amount of context after "Show All Context".

I'm referring to that area in general, but I'm talking about e.g. the src/applications/conpherence/application/PhabricatorConpherenceApplication.php section. The grey area above the diff shows

'/conpherence/' => array(

when it should say something like

public function getRoutes() {