D2 is considered toothy because of the chromium carbides it contains. There are several elements added to steel that have an affinity for carbon, iron is one, but it is not a strong carbide former and will form carbides, but if there are other stronger carbide formers, they will take the carbon and not leave much for the iron to form carbides. Chromium, tungsten, molybdenum, and vanadium are all strong carbide formers. Of these chromium has several characteristics that the others do not have. When present in high enough concentrations, along with some carbon, it will produce stainless steel, and when enough chromium and carbon are present the chromium carbides will clump together. The chromium carbides themselves have a great affinity for each other, they like to get together and throw a party
This is where the carbide clusters can cause a problem, since many of you are familiar with the micron scale, I will use that as an example; I have seen micrographs of chromium carbides in D2 that are 50 microns long and 25 microns thick. If you are using a .25 micron spray for the final edge or even a 1 micron spray, think of the huge difference in the fine edge you are trying to produce and the size of these carbides.
The toothyness of D2 is caused by these carbides being torn out of the edge during the sharpening process. They are very hard, if I remember correctly they are about 70 Hrc, and they will tear out of the surrounding matrix rather than being worn down.
There is a way to control these characteristics in D2 and that is to use CPM D2, this version of D2 is made by taking the finished alloy and while it is molten; spraying it out of a fine nozzel in to a cool vaccum, and that makes a very fine powder. That powder is then compressed and heated until it forms a single solid piece again. The temps here are pretty high, but not molten, and it gives a much finer distribution of carbides, so they can't get together and party.
In other alloys it can be controlled by lowering the carbon, such as in AEB-L , or by adding a carbide former that has a stronger affinity for carbon than chromium does.