Do you have an example?
I still have my vB forum operational on my laptop (with plugins removed), so I could take a screen shot of the feature:
However, I did have a plug in that would allow you to click the "63" above, or the number of people who viewed the thread, and then a window would open with a list of all of those readers but in chronological order, last reader at the top.
This was VERY useful as I could tell when someone read the thread, if it was recent or a while ago, without hovering over each name. If you could do this as well, that would make this add on GREAT!!