This picture really emphasizes the fact that Celestia was forced to banish her own sister. They were a couple centuries or millenia old when things started to get hairy with their relationship, and before then, they grew up side-by-side in the same household. If you have any siblings and have a close relationship to them, you would understand the pain she had to suffer. Banishing my brother... I could never imagine doing such a thing.
Oh man, at first I thought they just grew up together and suddenly combined into Celestia`s current form and then somehow there`s Luna again out of nowhere
and then I noticed the symbol on the darn moon in 2nd last panel! >__>
(...of which I then realized the actual consept of the comic; it`s not some random fanstory or anything, but the official story shortly). I indeed had a little different feelings than most of the folks seeing this comic.