as it was a little bit complicated to explain this missing feature in the Wednesday chat I made a screenshot so one can take a look at it. It allows one to store extra information for every user in the roster, for example birthday and phone number if one does not add it to its vCard for obvious reasons.
Oh, I did already create SPARK-377 (: you just need to schedule it for Spark 2.0.6 (;
One will see that the Spark window uses 8 times more space on the screen than Trillian. And the OnMouseOver popup is displayed outside the Spark window, so it needs additional space. If one sets the size of the Spark window to 900 using 1024x768 then part of the popup is displayed outside the visual screen. (<- little display bug without SPARK-issue)