I have spent hours debugging this but I can only conclude it is a bug. I am extending the threads route with my add-on. It has a dedicated [Home] tab and when that is selected and the index route is set accordingly (threads/featured), the session activity shows as "Viewing home". This works on every page except for the online list (http://xenforo.com/community/online/). There it shows as 'Viewing thread' but when the avatar is clicked from that page, it shows correctly as 'Viewing home' in the member card overlay. It shows as 'Viewing home' on the online list until another member views a thread, which is why it works on my local - as there are no other members. As soon as I log in to my local with another account and view a thread, it switches to 'Viewing thread'.