Duct-tape the "z" haunted comment panel mode back together

Summary: Fixes T3898. This feature needs generalization at some point, but just unbreak it for now since a surprising number of users like it.

Test Plan: Pressed "z".

Reviewers: chad, btrahan

Reviewed By: chad

CC: chad, aran, spicyj

Maniphest Tasks: T3898

Differential Revision: https://secure.phabricator.com/D7366