It depends. If the idea is spread by people understanding it and agreeing with it, then incomprehensibility is bad. But if the idea is spread because people want to feel pride in knowing something beyond the reach of most people, then incomprehensibility is a positive. The obscurity makes it a kind of intellectual "Veblen good".

But at that point, it's not being propagated based on its truth or usefulness, but merely as a form of signalling "I'm one of the smart ones". I suspect that at least part of the success of postmodernism is due to this.