Short

I feel like I should have read your last post slowly and carefully, but in case I don't manage to do that any time soon, I'll just jot down the first couple of things that came to mind while reading it. First a question - do you actually like horror? do you ever watch the films or read the books? One of the wonderful horror/ humor moments that comes to mind when thinking of the connection between the two (and I think horror movies that aren't on some level supposed to be comedies are rather an exception - Brain dead, dead snow, evil dead, Sean of the dead - they're all comedies), but the first creepy comic thing that comes to mind that works incredibly well is the scene from Mulholland Drive in which some guy comes into a fast food restaurant with a silly name - binkie's or something, and asks to see the manager... he wants to look out back because he saw something horrible in a dream, some sort of man/ creature that he would never want to see again. It's haunting him and he wants to reassure himself it isn't there. The manager is okay with this, and opens up the back and brings him out - it's broad day light in a safe suburban setting. The creature is there and appears to devour the guy. Both the comedy and the horror (which are largely dependent on timing and decor and probably don't come through in my description) are largely dependent on the absolute normality of the setting. The people, the surroundings, the outfits, everything is familiar and ought to instill confidence and a sense of security. The world is governed by laws which work off a basic exchange - a certain amount of security for a certain amount of freedom. When those laws are violated, the comic can result from the new found freedom, while horror results from the loss of security. Clearly this doesn't work for all humor... at least not the freedom idea, I don't think. But it is one interesting link. Funny the role murder plays in both... lack of restraint, exaggeration. Think of the scene at the end of Kill Bill part one when for what seems like forever the main character hacks through dozens of people with blood spattering in all directions - I laughed uncontrollably the first time I saw it. The violence was cartoonish because it was without consequence, because the people dying were not real people whose irrevocable loss I was aware of. A person not initially realizing they've lost a limb, or holding on to their own severed hand, once again potentially comic or horrifying, according to whether there are consequences, according to whether loss is internalized and permanent.
I don't think I've added much to what you said - it's an interesting topic. There's the connection between shrieks of laughter and screams of horror - waiting expectantly for something horrible or something comic to happen - audience members bracing themselves and making themselves consequently more susceptible to the desired effects (expecting something unexpected), though that's touching on cheap comedy and bad horror - I've never been much for the giddy variety of either.
In real life, genuinely horrible situations, humor often becomes a necessary defense... in my case at least, when I laugh at something upsetting, it is usually linked precisely to the liberation I mentioned before, a shift of perspective and a denial of importance or consequence to things that before something bad happened I might have seen as serious or even momentous. I have had moments where I suddenly had a profound sense that nothing could happen that was worse than death, and death, which is inevitable, isn't really that horrible... at moments like that, there is only freedom and real insecurity is impossible - the comic dominates absolutely.