I used to use a feature in VB, which I am missing in XF. In the default template of VB on every thread listing page, be it forum display or new threads, if we click on "Replies count", it opens up a popup window, which contains a tabular view of all the participants of that thread along with their individual replies count in descending order. If we further click on the replies count of any user, it closes the popup and parent page loads only posts from that particular user in that particular thread. I personally like this use case a lot and I would love to see this in XF as well (who knows, may be in a better way!).