wpDiscuz Online users addon is designed to indicate users online status on comment list. It adds online/offline badges on the right side of comment author name.
Addon checks all user statuses real-time and changes badges on comment list without reloading page. When a new user signs in (login), wpDiscuz Online Users addon displays a pop-up notification with just logged in user details (name, avatar) and last comment (comment intro and link to comment).
Addon also comes with many options and front-end style settings.