I'll assume you're using a jingum issued by the World HDGD Federation. I'd be confident taking a swing at a kitchen stove with those things. Some of the Japanese swords aren't as forgiving and will bend on poorly executed cuts. So far, I must have cut through some 20,000 or more bamboo poles without having a bend in my WHDGDF. The worst I ever got was a chip on the bottom half, from hitting the stand. On the other hand, my Japanese swords occasionally bent on failed bamboo cuts, especially in the 3" and over range.

The types of swords we buy from the WHDGDF are not the same quality as those used in Korea some 1600 years ago. Heck, they're not the same as the ones used even 600 years ago.

In Japan, there was/is a type of shito tameshigiri (blade testing) called kabuto wari or helmet breaking. Essentially a swordsman attempts to make a gash or "break" into the surface of the helmet. According to the book "Shinkendo Tameshigiri" by Obata Toshishiro, kabuto wari demonstrations were competitions between sword smiths & armor smiths. It logical that one can infer testing the strength of the helmet against a sword was necessary since attacks to the head were used in battle.

Please keep in mind that most of modern Kendo's major development was during the peace time of feudal Japan. A time when major battles did not occur often. Furthermore, it is currently practiced as a martial sport or for character refinement, rather than an effective method of combat.

Kendo does not reflect all JSA, both in terms of content & execution. There are several Koryu (literally "old school") that are drastically different from Kendo curriculum-wise. As for Kendo's effectiveness in battle, I don't think any serious Kendo student (10+ yrs) really gives that idea much attention. They train for the enjoyment of training, not for application in battle.

Re: type of sword I use.
I have used several WHDGDF jingums. Unfortunately i do not yet own one.
One of these days i will. 4 children sucked up all the money.

The sword i have cut the most poles with is a Cold Steel Warrior.
Not nearly as well balanced as a jingum, fairly tip heavy, but it's through hardened and tough as nails. Not a nick, curl, or any other kind of damage to the blade, and I've made loads of bad cuts, including through knots/joints. In fact I have NO qualms about cutting through joints in the bamboo, i've done it many times, the sword doesn't care at all.
And it makes a lovely sound, so it's easy to work on geometry.
I also own three different Cheness katanas, and am happy with them as well. Rugged and reliable. No edge damage on any of them either.

Of course I had a good teacher (Casey). That's probably the best reason I haven't bent any swords.

I will get a WHDGDF jingum one of these days, though. Hopefully within the next two years.

Yeah, I've heard of kabuto wari.
I would expect that was a demonstration of armorer's and swordsmith's skill, not a common every day event.
It would be a challenge to get a sword to bite into a steel helmet without fatally damaging the blade, given the uneven quality of their steel back then. Every sword was different. For that matter, there would very possibly be differences from helmet to helmet as well.

Are we underestimating the kendo 'snappy flick' a little? An experienced kendoka hits with the force of a freight train with what looks like a no effort or wind up at all...

I'm pointing out that you don't need the "force of a freight train" to cut an unarmoured opponent. It's not an issue of who hits harder; it's about how much force is needed to cleave flesh and/or armour. Since kendo targets areas of the body that are usually well protected by armour (men, do, kote), it lends itself better to unarmoured dueling as opposed to fully armoured battlefield warfare.

Sorry, then I misunderstood you...

Even as someone who does gumdo, I must say I think I'd prefer a long polearm or something on a battlefield...something that kept me as far away from the people trying to kill me as possible!

That's why bows are great.
It's really hard to block an arrow.

Ha!

I was told by my Kumdo (Kendo) master that a lot of techniques are different.

It was mentioned before could not be on top of the head - head strike would be at the neck side/temples.

Wrist strikes were on the inside to cut to avoid armor & cut the tendon.

Trusts were at the shoulder area in between the armour,to disable the arm.

Even Jo Chun Sa (Jodan in Kendo) would be different as the head armor would not allow the correct holding of the sword.

Even waist cuts in HDGD would have trouble with armor.

Yeah, jochunse doesn't really work if you have a helm or bulky shoulder-plates. I've seen people bring their sword to their right side in a vertical stance, a-la-palsangse.