It made Kurt unhappy that old rivals of his were around again, but this time they were in his shadow. Because of this, he made several negative comments about Pearl Jam in the press. Kurt softened up later on and was developing a friendship with Eddie Vedder towards the end of his life. Contrary to popular belief, Pearl Jam and Nirvana are not arch enemies, and all members of Pearl Jam were devastated by Kurt's death. Kurt was either participating in the joke, or was poking fun at Eddie for misspelling the band name.
Nobody knows for sure.
Eventually, he was caught and sentenced with community service, and he was told not to tag anything else. It can be seen in the SLTS video. He is Tony, a friend of the band. First of all, there is no application to fill out or some alternate way to become one. Sometimes a new moderator is picked in a democratic fashion where a thread is created in the Junkyard forum, asking who should be a mod.