OK, it seems my first question got answered very clearly. Now I wonder how Ni nostalgia would differ from Si nostalgia. Less details? A surreal memory?
I'm quite idealistic, but I'm not nostalgic at all. Well I might have been originally, but I have become pretty good at staying present in the moment, and if I'm present, stuff from the past can't really affect my emotions.
I dislike the feeling of Nostalgia so I usually don't dwell upon my memories. There was a thread in the INTJ forum about how Ni is connected with deep feelings of nostalgia.