Debate.org opinions should be questions because that is what a debate is! You can't debate a statement or give an opinion on it as easily. The whole point of this site is to see the opposite side of things, and you need to have a question to get that opportunity.
Does it really matter if Debate.org opinions are in the form of a statement or a question? As long as the debate writer is sticking to the topic and getting their point across, what difference does it really make? Sometimes statements get a point across. Other times questions are better at making people think. Can't we allow the debater to make their own choice?