It occurs to me that Chat would be a fine place to get to know your fellow SE users a bit more, by enabling the rapid eXchange of... thoughts and ideas.
But this presents a problem: users are scattered across the globe, with wildly varying times of activity. Some of us get up at the break of dawn and chat while drinking our morning coffee, while others wake at dusk and chat while sucking the life essence from their evening's victim. Attempting to use chat across such barriers can be an exercise in futility!
Furthermore, some topics themselves have regular periods of low and high activity. For instance, most users tend to visit The Tavern in the morning, while later on preferring to discuss their bedtime bacon.
Therefore, I propose an addition to the information displayed for both users and rooms: daily activity histograms:
I envision each graph representing a day, with each bucket representing the sum of an hour's worth of posts. This would be most useful if no more than the last week or so of data was used for each user or room - curiosity on long-term historical trends could be sated elsewhere. My goal here is that users would be able to identify at a glance the likelihood that their target will be active, and plan accordingly.