There's something about read indicators that always gets under my skin, and I'm not entirely why. Partly it's because it works against the idea that chat messages should be treated asynchronously, but It also feels kind of invasive? Like my device is tell on me for being indecisive or anxious about responding. Maybe I'm just weird but I've alway been curious how others feel about that. The snapchat style "currently viewing" indicator makes that even worse.
That said, the timeline and quick switching ideas are very cool. So many chat apps implement a text search and stop there, this is a clever way to find a specific point in time, or find specific non-text content.