Okay, sooo I think this is what they mean....
key work THINK.
say there's a forum post with a group of people responding to people,
you'll get notifications IF they either direct respond to you by tagging you OR literally hitting the respond button to the spot you actually typed. So if you me and Joe Schmo were all in this message group right now and I went to go respond to you technically but actually hit the reply button on his message instead, unless I tag you, you will NOT get a notification.