Why "Call me Ishmael" is a great opening line and a good joke as well

In looking up some obscurity yesterday I noticed a blog entry or website or something that asked: Why is "Call me Ishmael" considered a great opening line? Didn't read the entry, but here are several reasons. First, it immediately establishes the narrator as someone factual and direct and in direct contact with you the reader or listener - it's an intro, but also an imperative sentence, much stronger than, say, "My name is Ishmael." Yet, second, it's a bit of a misleading line. In fact, as we learn from the second sentence, about the dark November of my soul, I think, that this is a loquacious and highly stylized narrator. Ishmael narrates the whole novel, I believe, but he vanishes into his own narrative: he recounts all that he sees, learns, and knows about whaling and about this whaling expedition, but he plays no role other than narrator - he himself has no bearing on the plot. So why is he telling the story? Because (as we learn at the end), he is the sole survivor, the only one who can tell the tale with credence. Yes, Melville could have used a 3rd-person, omniscient narrator, but this Ishmael guy makes the story that much more immediate, direct, and personal - yet by being so removed from the plot, he makes it universal as well: it's his story, and everyone's (anyone's). What a strange first sentence, though - especially in that over the course of the entire novel, I'm pretty sure, nobody actually does call him Ishmael. I don't believe there's ever a line of direct address or a conversation that captures his name. So perhaps it's not his name? Perhaps he asks us to call him Ishmael so as to protect his real identity, which is ... what? Herman? Or it may be as good as saying, you might as well call me Ishmael as anything else, because I have a story to tell and my name won't make a whole lot of difference. All this setting aside the more obvious theme of the Biblical Ishmael, the less favored son sent off into exile and perhaps taking up life with a rival state and founding a (rival) line of his own: I don't see any direct correlation there except that adopting or announcing the name Ishmael sets this character, and this story, as one of exile, cursedness, and loneliness. As a final note, there have been playful takes on this opening line, including the opening of (I think) a novel (possibly by Irwin Shaw? not sure) that begins with two men concluding a conversation on a NYC street corner and one says to the other: "Call me, Ishmael."