User blog comment:Dopp/Technical Updates: November 1, 2011/@comment-3569803-20111101191811/@comment-1656630-20111101192145

Yes -- it's light this week because our engineers were focused on "small stuff week", but there's one big change: Timestamps will show when a message was last edited, and clicking that will take you to the message-level history. More kinds of history coming soon.