Fixes T2523 - Comments are being displayed in feed.

Summary:
currently, only comments per se are being displayed. cut after 128 characters (which is the default), means in theory up to 128 newlines ^^

when you for example claim a task with a comment, close it with a comment, or do anything else, it won't be displayed

Test Plan: {F33890}

Reviewers: epriestley, btrahan, hwinkel

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2523

Differential Revision: https://secure.phabricator.com/D5119