Yeah, definitely a good point. Curves do make aiming a thrust more awkward, which proves an inhibiting factor.
Depends on what you are used to. Training is an important factor. I tried both of them and didn't saw much difference, except that if you use the curve correctly it can work to your advantage as the point is harder to parry when it actually wraps around your blade.
Agreed, the same way the cutting power of a straight sword is not something to me ignored, but when thrusting is a must you don't choose a Katana or any curved blade; it is a matter of geometry and physics.
Actually the stiffness of blade and the angle of penetration may have more to do with this than the modest curve of a katana. I will refer to the same test by Michael Edelson to disprove the myth of the poor thrusting ability.
That's a Japanese sword design introduced in 1934, you see the European handle? It was a lot more efficient than the traditional handle for that kind of swords but... soon after they changed it back to the traditional handle. why? Tradition NOT innovation or efficiency.
Don't go think that fascist Japan was the same as feudal one, Japan was profoundly changed by the Meiji restoration. In the 30's, Japanese government was trying to uphold "traditional" values (at least what they thought would be) to give moral high ground to their soldiers. Having traditional elements in their swords and equipment was one of those things.
The Japanese were actually known for their openness to new concepts, they adopted European firearms and modified them (to the extent that Chinese soon preferred Japanese matchlocks to Europeans one), same things with armors that Japanese armorers didn't hesitate to replicate and modify it for Japanese tastes (adding parts mostly and different artwork). We could add religion, ships, scientific and political concepts. The list is rather long. And we don't even talk about Meiji Japan who transformed a medieval country into a modern military and industrial behemoth in 20-30 years. Who says strict traditional society? Actually the Meiji government is responsible in most part for the rigidity and the conformity we normally stick on Japanese culture (from my experience I would say it's not really true outside of Tokyo), mostly to imitate Victorian values of the time. Japanese before then were not seeing themselves as a country, nor did they spoke the same language or had the same customs or way of doing war. Meiji wanted to change all this to create a unified Japan, and mostly succeeded.
I mean, they even try as much as they could to avoid the use of firearms, trying to isolate their country from foreign influence.
Hum... which period? Edo period? Because in the 16th century Sengoku period, one single army in Japan had more guns than all France or England. They also developped strategies to use them that wouldn't be used in europe before aother century. At Nagashino. 38 000 soldiers of the Oda clan were present, 10 000 of them were gunners. And the battle of Komaki was actually one of the first trench battle, where soldiers dug their position, firing at each other, nearly no melee fight was made. Did I heard strict traditionnals or myth debunking?
Now if we talk about the Edo period, that's another thing. Firearms were not of much use because first they were highly reglemented, and there were not many wars for them to be used. But that's the official side of things... We know that smuggling was not efficiently controlled by the shogunate, as the Satsuma clan had modern cannons and guns that actually impressed 19th century observers. It is even known that in 1725, the Yoshimune shogun invited Hans Jurgen Keyserling to teach modern horseback riding and fighting to his men. Again, traditionalism?
Or just considere the Tanto! most of them are single edge when, obviously, is much more efficient as a stabbing weapon a double edge straight blade.
Actually most tanto were straight, even more so when we talk yoroi doshi (armor piercing daggers, here is an example from the 17th century, two edges, perfectly straight, very obtute:
http://www.japaneseswordsltd.com/yuridoshi1.jpg). Some had two edges, and spear points were often used as blades. As for the double edge, it is not a norm. Many rondel daggers have one or no cutting edge. All techniques I have seen when a tanto is used against armors are aimed at the same weak spots that appear in european armor (armpit and neck mostly).
As for the wood in Japanese armor, I have never seen or heard about this from even top researchers in the field, nor have I seen anything else than metal armor and very rarely leather. I don't know what's the exact reference but I suspect they mixed up with training armor (bogu) or even prehistoric armor.