being that harsh doesn't make you sound smarter, it doesn't prove you right either, please stay polite.
yup carbon AND alloying elements are parts of the story, but when it comes to comparing steels, not finished knives, they are the biggest part of the story. along with the fabrication process. this is comparing steels one can also heat treat S125V to 50hrc and it will be tough ... but i'm not making stuff up saying than the more alloying elements you have in a steel the more brittle the steel will be.
i'm pretty sure that whatever i say you will say i lie because you sound pretty sure of what you say, sure enough to be rude. no i'm not making anything up.
so i quote from KF "in the kitchen section". a few generalisation from larrin thomas (devin thomas' son, metalurgist) who is know for making stuff up ... here is the link so you can see i'm not making up the quotes too ...
http://www.knifeforums.com/forums/showtopic.php?tid/809833/
The following steel information was written by Larrin Thomas)
Carbides – Simple explanation: Hard particles formed in steel when carbon forms with iron or transition metals.
In depth: Carbides control greatly the level of wear resistance and toughness in a steel. Because carbides are extremely hard, a great volume of them will make a steel very brittle, especially if the carbides are large and unevenly distributed. Steels vary from nearly 0% all the way to 30% carbide volume.
oughness - Simple explanation: Ability to resist chipping or breakage.
In depth: Toughness is controlled by amount of carbon in solution, the hardness the steel is heat treated to, the carbide size and volume, and the other alloy in solution. High amounts of chromium weaken grain boundaries (though generally carbide size and volume is the limiting factor as far as toughness in stainless steels). Nickel and silicon in moderate amounts increase toughness without effecting strength. Carbide size and volume are probably the greatest controlling factor for toughness.
he must be making stuff up too ...
edit just to clarify i spoke about edge stability wich you seem to have mixed up with edge retention. they are not the same thing there's a small explanation for that on the link i provided. edge stability is more boound with carbide volume than carbon content and is somewhat related with toughness.
that's not my knowledge, that's from someone who spent years learning about steels and that's only simplification so US knife users can understand what we talk about. but if YOU know more than HIM, then sorry.