Summary: Adds commenting to Phame Posts, also testing a new "document comment style". Unsure about it but Phame is a prototype so good place to explore.
Test Plan: Leave some comments, see some comments, test show/hide.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Maniphest Tasks: T9746
Differential Revision: https://secure.phabricator.com/D14451
