First of all, I'll say that I agree somewhat with Ebert's definitions, but I find them rather constrictive. Comedy is much more layered and nuanced than what those two definitions describe.
I'll paste my response here which is a response I gave on another board when the question of whether or not people agreed with the statement that all comedy comes from tragedy.
It doesn't address, specifically, your question, but it gives my view on comedy in general and how it works:
"Whoever first said that comedy comes from tragedy didn't think that statement through very well. Of course it does, but there's much more to it than that. Besides, tragedy and "sad" are in the eye of the beholder.
Comedy comes from a violation of expectations (or a familiarity with those violations), not simply tragedy. Humorists take these violations and play with them, manipulate them, exaggerate them, etc., for laughs. Even humor based on negative stereotypes (rednecks, certain blacks, certain whites, etc.) is based on the fact that the stereotype itself is a violation of how we feel someone "should" be or act.
Take some of Jeff Foxworthy or Jerry Seinfeld's humor. Seinfeld built a career on making jokes about "everyday" situations. Even in his TV show (which, admittedly, had a lot of absurdist humor in it) he had those jokes. Such as his date who had "man hands" or when his girlfriend dumped him because (due to the angle) she thought she saw him picking his nose in the car. The episodes about not remembering his girlfriend's name and his other girlfriend who appeared horrid in one type of light but beautiful in another are other examples of this.
Jeff Foxworthy's "You Might Be a Redneck..." humor made him millions by parodying rednecks and Southerners. I always liked, "If you have to climb to the top of a water tower with a bucket of paint to defend your sister's honor, you might be a redneck."
Chris Rock has built a career out of satirizing everything from gender differences to racial stereotypes. And satire is basically humor pointing out the discrepancies of logic contained in what people do and/or say (violations). I can watch Chris Rock and laugh my a$$ off because the things he says are so funny, because they're so true and familiar (in many people's eyes, at least).
We've all encountered these things (to one degree or another) and can all identify with the familiarity of them (of course, when we first encounter these things in our lives, they are originally violations of our expectations. Only later do they become familiar).
Tragedy is a violation of expectations (albeit a sad, negative one), otherwise it wouldn't be "tragic." Farting in bed is another one. As is a horse trying to spontaneously mount a reporter (saw that one on a blooper show once).
Comedy isn't based on "tragedy," per se. It's based on violation of the status quo from which we derive our expectations.
Without these violations, there would be no comedy"
Basically, the comedy writer takes these violations to the extreme and (sometimes) exaggerates the heck out of them in order to get the laugh.
I think, in terms of what Ebert said, the "what" comedy isn't as enduring as the "why" comedy. For me, the "what" is simply a cheap gag; a throwaway attempt at shock or humor. Basically, you see some funny gag in a movie and it's forever deflated. The "shock" of the gag just doesn't seem to have the same effect with repeated viewings. This is true, for me, with the movie "Me, Myself, and Irene" (and, pretty much any Farrely Bros. movie). The rarely rely on character development of comedy and instead rely on cheap gags.
However, sometimes the "what" comedy is great. "Team America: World Police" has a lot of "what" comedy in it (the sex scene in the unrated version) that keeps me laughing (though, admittedly, not as loud as the first time I saw it).
I don't think that either type of comedy is more funny than the other initially but, over time, one type does seem to stick with me longer; the "why."
The "why" type of comedy, I think, comes more from character and the situations that the character (by his/her nature) winds up in. This is the type of comedy I find the most enduring because the story is crafted in such a way that we become involved in and empathise with the character, therefore, no matter how many times we see the movie, when a "why" situation comes up, it's still funny.
"Forrest Gump" is a good example of this. The humor in that movie is more "subtle" and "cute," but it is mostly based on character. So, everytime I watch that movie, I always laugh at the same spots (dialogue, usually).
Having said all that, though, I think the best comedies expertly weave both the "what" and the "why" types of comedy together. A great comedy isn't one or the other, it's both, and it's always based on character, not just thrown in there randomly.