This makes sense to me. D2 has a natural tendency toward latticing anyways, and so likely your hard batoning found a lattice point and the clean break occured. This is much the same as how diamonds are cleaved.
This is also why most service swords aren't made out of real hard/inflexible alloy. A certain amount of hardness balanced with tensile strength is what's desired in a bigger blade. You don't need a lot of flexion in small blades like what folders are made out of, typically, so it makes sense that they would be from harder, more rigid material. Tool steel is made for precision, not for manipulation. D2 is a tool steel. This is another reason why mower blades are made pretty soft. If you had a lawnmower with a D2 blade, it would explode on impact with the curb, the sidewalk etc, rather than just burr up the edge some.
I think metallurgically we are at perhaps the limits physically of what can be done with metal. We now have such things as dendritic cobalt blades, crucibled composite blades, differential heat treating, cryogenic hardening, nitrogenation, and every possible alloying formula across the periodic table. Short of hiring a group of elves or dwarves to start putting +1 attack features onto our stuff, it is about as good as it is ever going to get. Besides, I haven't seen any vorpal bunnies or short ugly hairy footed dudes with mithril armor running around lately. I'd say that the next big improvement will be in educating people how to use and maintain the blades they have, which to me means opening the history books and re-educating people about how guys with standard issue carbon steel blades conquered the frontier countless times past. Yeah, maybe they didn't have to stab through car doors or chop through 10p nails and such, but they did carve up an awful lot of wilderness. The best $300 blade out there won't be worth a tinker's darn if you don't know how to use it right. Now that you know how D2 fails, you've learned that sometimes the best uber-metal on the market isn't the best choice, and so we go back to what we know works, having learned an important and somewhat expensive lesson perhaps. Kudos to the Falcon for stepping up and sharing his experiences here with us so we don't have to repeat the lesson ourselves.
It makes you wonder sometimes how not-so-ancient man got by with glass and stone blades. Can you imagine chopping down an oak with a copper headed axe?
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)