Comedy v. Tragedy

In my writing this current post, you will have to forgive me for two things: A) for trying to extrapolate what may or may not be a major theme of a 1000-page novel from a single sentence, and B) for drawing most of my conclusions from last session's section of the book, since that's what I've really had the time to think about. I've been trying to squeeze all of this week's reading into the last few days of the allotted time, which isn't leaving me too much time to truly analyze it.
I did, however, do a fair amount of thinking about last session's reading (admittedly, a lot of it was on the train ride home from our last seminar day.) In my last post, I didn't want to make any stabs at analyzing themes in case I happened to get it all horribly wrong, so I focused on the erratic writing style, but now I'd like to make the attempt to discuss a possible major theme.
I would like to form this entire post purely by taking a single line and connecting it to the title and generalities of the book. Last week (or two weeks ago, whenever it was,) when I reached page 71 and read the sentence, "Nor that jokes and sarcasm were here usually too pregnant and fertile with clinical significance not to be taken seriously: sarcasm and jokes were often the bottle in which clinical depressives sent out their most plangent screams for someone to care and help them," one of my first thoughts was "hey, I wonder if that's the whole point of the book." Now, given the amount of book and how many proto-themes we've seen developing (by which I mean the seeds of what may turn into themes over the course of the book) I would consider it more than unlikely that this is literally the entire point, but I suspect that there may be a major theme here.
In my mind, this line signifies that everything that we percieve or put forward as comedic actually can be horrifying, sickening, or depressing. I certainly think that this is true; I think that being amused, being horrified, and being nauseated come all from the same root-- something not being right, something being twisted out of all normal order. This is certainly true of the novel's first chapter, wherein Hal is talking to the university deans, and the following chapter about Erdedy's addiction. I read both these chapters originally with primarily a sense of horror and sympathy for both characters' situations, but in a different mood, such as many of you clearly were in when you read it, I might have just as easily responded more to the humorous exaggeration and phrasing. This probably holds true throughout the entirety of the book, as far as I can tell. The scenes dealing with the medical attaché and how he is rendered helpless watching a cartridge started off puzzling me, then somewhat horrifying me, and ultimately quite amusing me as he continues to stare blankly ahead, so dominated by the teleputer and so dependent on his wife that he begins to soil himself as he sits their pathetically. If anyone has any more evidence, such as anything from this week's reading, that particularly supports or refutes this idea, why not post it as a comment on this post?
I'd also like to bring the title into this. Infinite Jest suggests a comedy, but the scenes depicted in it are horrifying. Mostly, the title simply leads me to think he has something to say about comedy. I also find it interesting to note, as Sean did with his post last week, that the phrase "Infinite Jest" seems to come from Hamlet; the title which leads us to think about and expect comedy is, in fact, drawn from western culture's most famous, and arguably, best, tragedy (by the way, another tidbit of support for this origin of the title is that one of the films in Incandenza's filmography is produced by Poor Yorick Entertainment Unlimited). I think that every time you pick up Infinite Jest, whatever mood you happen to have at the time dictates whether you percieve it as hilarious, tragic, nauseous, or horrifying.