I also saw an earlier reference, too, maybe on the very large discussion thread somewhere. But the problem for me is that Melville’s Ishmael is an observer, not an actor or an avenger. In the end, he plays the role of one of Job’s servants, who reports back with word of the disaster, which was caused by the monomania of Ahab. I don’t think a crazed killer would take him as a model.
It wasn’t Moby Dick. I don’t remember what it was and American lit isn’t an area where I would claim any expertise at all, so I can’t be of much help.