I would give Zen a call. DLC shouldn't have this problem. sounds like an incomplete coating. It happens! It is a very, very hard coating. Almost indestructible when properly applied.
The "don't use soap" confuses me. It is used quite a bit in the Watch world, (High End) and used in salt water diving, and all kinds of bad environments. A little bit of soap should do Nothing if the DLC is properly applied in multiple layers.
I've seen many watches that have been worn for years, without a mark on them. And a watch gets a LOT more abuse than a tank for most people. And we all use mild, (dish Soap) and water to clean the watches. Never heard of a single problem from any one doing this with DLC coatings.
I'm wondering if ZEN is simply using typical PVD coating, rather than the full DLC version. He states that it is next to diamond in hardness, and this only describes the DLC version. Strange!
In fact, DLC stands for Diamond Like Coating.
so the question is, is Zen using the very common PVD Coating, or the more complicated (and expensive) full DLC- PVD coating?
In watching his "To Destruction" Test in Part 2 of PBusardo's vid of the Zen interview, one could conclude that it is indeed DLC. If turning at high speed on a lathe, and applying sandpaper of differing grits to it does nothing but polish it, there is no way simple every day carry (in such a short time) would show any ill effects.
I have some DLC coated end mills here in the shop, that have repeatedly,at high speed, cut through very tough high grade Jet Turbine steels, and show NO Wear whatsoever. I seriously doubt that simply wiping it with a paper towel is going to damage it. LOL
I would definitely give Zen a Call. Something is amiss here. and with Zen's penchant for quality, I think he will be more than happy to take a look at the problem.
Knife