Add an unread class in the inbox

Quoting from 💬 Automatically scroll down to last message when message thread is opened Active :

Why isn't there any "last" class at class="private-message-wrapper" ? How can I add it?
Why isn't there any anchor link to the last message in the thread? How can I add it?

This is a more complex issue. If we put a class on the latest we should remove it after the user has seen the message. Say after 3-5 seconds. But if the list is big, some of them are not visible (because you'll need to scroll), so the JS code should be clever enough to remove only the classes form messages that were scrolled into view (with a delay of 3-5 secs). If we still need this feature it should be split in a new ticket

I see this is already in place. Unread threads get an unread-thread class. Closing.