6:15 PM
@Xanne you have to add some fluff after the reply so it pings the person you want to reply. Just the reply button won't work. For example, my message below doesn't ping you.
You have to type it out. Though, that must be a pretty old message you were replying to, judging by the message ID.
Huh, it was that message. Weird. Maybe a browser cache thing.