When I saw this...
...it kind of registered as being Aang for a split second before I realized it was Jinora.
I also noticed that she knows an awful lot about the library. I wonder if there's anything to that. At first I thought she might be a reincarnation of someone who was there and she was somehow aware of that.
With Korra having to learn here how to control her anger and look for the light and peace inside her, I think this is going to end up with her taming Vaatu, convincing him and Raava to rejoin in balance.
If that comes to pass, I wonder what it means for Korra as the avatar.