This should be added for staff now. My biggest concern with the current addon is it'd display the checkmark even if the user has their activity disabled, which is not something I'm fond of. I'm hoping to add it in the future for everyone but I need to find a way for users to disable it via their account settings first. Users should be able to pick if they want that information visible or not in the same way it's an option for threads and so on. So I'll look around until I find something better.