The word "nice" with several appended "e"s includes a degree of "
niceness" to the original phrase. It is used in online
chats to
indicate strength of the usage of the word without using modifiers such as "very" or "quite".
DudeA: "I just finished my
homework."
DudeB: "nicee."
In another situation:
DudeA: "I just
rooted the
NCSA!"
DudeB: "niceeeeeeee!"