My own opinion is closer to Cheney's. I think it's important (and more than that, helpful) for a writer to know the rules. I don't think following them is important.
Trent talks mostly about the importance of consistency of character. But people do what people do, for whatever reasons they do them. Anything can happen in fiction. That's why it's called fiction. If it's compelling, I'll read it. If I care about the characters, I'll go along for the ride, even if they do things that may seem unpredictable, strange, or seemingly inexplicable.