My highschool debate experience taught me to recognize some 'cheap debate tricks' in rhetoric, but the sad truth is they exist because they work. Most of my judges at competition were volunteers without any particular training in rationality or logic. In one debate where the resolution was something to the effect of 'the use of nuclear weapons is always unjustified' (in which I had the affirmative) at the end of the debate the judge gave a speech about his time in the Pacific during WWII, and how his he and tens of thousands of his compatriots would've all died if they hadn't dropped the bomb when they did, concluding that no argument could convince him it wasn't justified. There is no way this caliber of judge is going to spot even basic fallacies.
In general, the form of debate instruction is just a toolkit for effective motivated reasoning. The pre debate research is all about amassing facts that support your position, and to the extent that you also have to be aware of facts detracting from your position, it's only so you can research counterpoints to those facts, or otherwise discredit them. The debate itself is an exercise in whatever the opposite of active listening is; don't take the opponent's argument as a whole, or understand their position in any deep way, just listen to idenify the tiniest inconsistencies or errors, then pull them out of context and attack.
I don't know how it could be improved, maybe if instead of convincing a judge who is not particularly informed on the topic, the goal was to arrive at some kind of consensus? Instead of modeling presidential debates we model supreme Court opinions? Everyone has to try to write a position that actually gets other people to sign on? There are certainly some insensitive issues that would need to be overcome, but at least the focus would be on broad ideas rather than nit-picking, and each contestant would need to think about convincing other high-information participants rather than the lowest information one?
Never done this kind of formal debating, but it feels like the main skill you learn is the exact opposite of rationality: give up caring about an accurate description of the world in favor of extracting the most personal benefits from a preset view.
I'm sympathetic with that view, but think it's far from clear-cut. For example, suppose you model rationality as the skill of identifying bad arguments plus the mental habit of applying that skill to your own ideas. When the former is the bottleneck, then debating probably has a positive effect on overall rationality; when the latter is the bottleneck, it is probably negative. Probably the latter is more common, but the effect of the former is bigger? I don't have a strong opinion on this though.
As an anecdotal point, I have been pleasantly surprised by how often you can win a debate by arguing primarily for things that you actually believe. The example that comes to mind is being assigned the pro-Brexit side in a debate, and focusing on the EU's pernicious effects on African development, and how trade liberalisation would benefit the bottom billion. In cases like these you don't so much rebut your opponents' points as reframe them to be irrelevant - and I do think that switching mental frameworks is an important skill.
There are two distinct parts to this.
1) does competitive debate do a good job of truth seeking (and/or can it be reformed to do so). I'm with many commentators in that I suspect the answer is no. The format is just not suited to it.
2) do some of the skills of competitive debate aid in truth-seeking outside of such debates. Probably, but I suspect those skills come along with habits and attitudes that make them less effective in truth-seeking than if they were learned elsewhere.
To be fair, debaters are aware that the existence of convincing rebuttals doesn't necessarily invalidate a claim. But motivated reasoning can be a powerful force, especially amongst intelligent people. This is particularly true when you've been trained to respond oppositionally to any claim that doesn't support your current position. I can think of several cases where I've been able to ignore a nagging voice of doubt by quickly finding a plausible response that turned out to be incorrect. The social media filter bubbles that we all currently inhabit can amplify this effect by caching in your mind hundreds of examples engineered to be memorable and stoke outrage; to counter it, it's more important than ever to genuinely consider opposing arguments rather than going to the automatic rebuttal mode that debating ingrains.
The other thing that debating (arguably) does is cultivate a non-empirical mindset. At the end of the debate, the question isn't settled. There may be more clarity over exactly which factors might swing a conclusion one way or the other, but almost nobody ever bothers to go out and do that further research, or even fact-check claims made during the debate - despite the fact that it's now easier to access such data than ever before. Of course if you asked debaters explicitly they'd be clear that empirical results are usually required to actually draw firm conclusions. But if you spend long enough thinking and arguing in a certain way, it's difficult to imagine that it doesn't carry over to your reasoning in general.
At this point I want to be a little speculative. I'm not sure whether the issues I discussed above can be addressed within anything resembling a traditional debate (I'd be interested to hear your comments on this). But let's say that we want to design an entirely new form of debating which instilled the best possible habits of thought. What could it look like? It would need to be driven by empiricism, while still having room for conceptual analysis. It would still be fun and competitive, but debates would also build up the sort of knowledge which could actually help drive decisions. Domain-specific knowledge would be helpful but not essential.
This was in the back of my mind when I read about two very interesting studies. The first was by researchers at Uber: they calculated the willingness of consumers to pay for Uber rides by comparing times when the calculated surge index was very similar, but the actual surge price was different, e.g. 2.24 vs 2.25, rounded to 2x and 2.5x price increases respectively. The study was heavily criticised for equating willingness to pay increased surge prices with overall "consumer surplus" created by Uber, but the initial methodology was still quite clever. The second studied Italy, which is apparently the bank robbery capital of Europe. Researchers analysed the relationship between duration of robberies, amount stolen, probability of being caught and prison sentence. Their hope was that there would be some consistent tradeoff between the expected gain and expected punishment; it turned out that more capable robbers behaved as if they assigned higher disutility to prison time than less capable ones. This sort of creative approach to answering important questions is something we sorely need more of; let's consider a new form of debating, neodebating, which is aimed at encouraging it.
The core ideas underlying neodebating would be that, instead of debating about what is true, we could debate about how to find out what is true; and instead of debating what the effects of a certain policy would be, we could debate which policy would best create certain effects. In some debates this would look like both sides designing experimental methodologies like the ones I outlined above, then critiquing and defending them. In others, it would require teams to dream up specific interventions, e.g. "What's the best way to build stronger community spirit in deprived areas?" Debates could focus on personal decisions: "Your best friend is going through a midlife crisis and feels like their life is meaningless. What do you do about it?" But they could also be about some of the biggest modern issues: "Redesign the education system to make it as effective as possible in conveying skills and knowledge." These debates would be judged on the current standards of persuasiveness and eloquence, but also on creativity and boldness. The most fun debates I've ever done are the ones which introduced me to totally new ideas: in an ideal implementation of neodebating, every debate would be like that. And I think the mindset required is exactly what we should want from political leaders - an innovative, experimental approach to finding the best policies, plus knowledge of how to test and evaluate them. It would even promote the statistical literacy required to identify and argue about correlation, causation, confounders and controls. Wouldn't that be great? If I were being really idealistic, I'd even build in a mechanism for teams in a debate to make bets about relevant future events, with points awarded retroactively to whichever team turned out to be correct.
Anyway, enough daydreaming. For now, I think my main point is that everyone - but debaters in particular - should spend some time answering a few questions. Which arguments do you critique most rigorously? Do you ever try to generate novel and creative solutions to big problems? Do you seek out enough empirical data? And when and how do you actually change your mind?