What a line! Consider: what if you do everything right, make it to heaven, and it is more unbearable than a hot day at sea? Radiance? Could an eternal reward turn out to be too much of a good thing? How should mortals prepare for an afterlife of forces beyond their comprehension?
Winston, my wife considers me a human aberration because for me no temperature is too hot. On the day we were married, it was 108 degrees. She was miserable but I was thrilled, and I took it as a good omen (which it so far, almost 10 years later, seems to have been).However, I am intrigued by your inquiry and one of the many reasons that I love this novel so much is that it is full of the same kinds of questions. Fedallah is one example. Is he some kind of demonic force leading Ahab to his death or is he, as he hints at, a servant of God ridding the world of the monstrous Ahab? Is the whale, Moby Dick, a dumb brute of an animal, God's will made flesh, a force of evil and destruction, or something else? In this one line, and in your comment, you are scratching the surface of the almost endless questions Melville raises. Good stuff!