CD: The notebook/story/dwarfs are discussed in little bits throughout the VN. The whole thing is a huge symbol of the Little Busters - the people themselves, the story, and the transcendent being that is the Little Busters. They really could have done a better job with focusing on these more so there was more effect when Rin found the notebook in Refrain, because it could have meant so much more to me. But anyways, its a great ānot a spoiler unless you know its a spoilerā, and has a bunch of meaning, so its fitting for the OST cover.
Game cover: That scene is pretty much a secondary climax to the whole story (at least it was supposed to be). And it perfect for the cover since its another ānot a spoiler unless you know its a spoiler.ā So if youāve read the VN, you see the cover and remember the scene and remember the meaning behind it; and if you havenāt read the VN, it looks like a scene that might be important, but it all doesnāt reveal anything at all.
Komariās importance is probably the biggest screw up of the entire VN IMO. Its very clear to me that the scene with her and Rin on the rooftop was supposed to be very meaningful, and that she was supposed to be Rinās best friend. But they didnāt really have much build-up with Rin or Komari previous to that scene to show how they had become friends and how Komari had helped Rin.
I would say that her intended importance, though, was to be the one who truly helped Rin to become strong, and to be able to live on when the āWorld Where Nothing Happenedā collapsed.