R1:61f5461e6de9

Fix Conpherence CSS (mostly revert)

Summary: Fixes D7669

Test Plan: test many participants and many threads in Conpherence, mobile and desktop.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7696