Honestly I think that if you write a big enough horror story, there's going to be comedy that comes out of it. It's required to break the tension. Plus the atmosphere sets up comedy to be the least expected: something that always makes jokes funnier.

Having humour in a horror story doesn't take away from the horror. I would tend towards categorizing your work based on what will warn sensitive readers of what is the thing you're most worried they might be turned off by. Nips the whole issue in the bud.

Nobody will complain about reading a joke in a horror novel. But you can certainly bet someone will complain about reading horror in a comedy novel.