Also, if you are creating a thread, you can tailor the opening post to take into account the people already online, to get the conversation rolling immediately.
I'm using Firefox on a mac. I've checked on Chrome, and it's working for me. Edit: I think the feature has been amended to allow for active users when you look at the main forum, but it won't show which posters are viewing any specific thread.
I think you're right and they must have just activated this as it was working yesterday. What's the point of this? It was useful to see who was viewing the thread.
We turned of active users in threads yesterday to see if it helped site performance. We are discussing what features to turn on or off here: https://www.bigsoccer.com/forum/showthread.php?p=22004422#post22004422