Here are the steps to reproduce.
1) In the Roster tool use the search box and type in part of someone's name or ID. 2) Use the down arrow key to select the correct name. Instead of a single name coming up, you'll see multiple copies of the same name in the results screen.
Please note that you cannot reproduce it if you use the mouse to select the correct name from the drop down list or just click the Find button.
It's very strange. I attached a couple of screenshots of what it looks like. Same behavior in Windows and Macs with Chrome and FF on 12.x and 20.x
Although this is a minor issue, we thought we'd better let you know.