Pete, I think it's tempting to claim that one might lose some food release, but under almost all circumstances the variation in geometry is subtle and shallow enough (unless there is an intentional compound grind which is usually much deeper) that it likely has no real effect on food. Near-edge convexity, bevel polish, and the primary shinogi are much stronger influences on sticking, in my opinion. Raising the shinogi too much can affect things by reducing its angle (allowing food to slide over more easily) and increasing surface area that contacts the food directly. Otherwise, I doubt flattening (and some convexing if applicable) are in any way harmful to the cutting ability of the knife.
Further, knife geometry can be wildly inconsistent even from the same maker, such as the Carter shown. This is
usually not extremely nuanced stuff.
Rami, most knives like this operate on relatively simple geometry, unless we talk about convexing near the edge. There are some knives that implement a hollow (accidentally or intentionally) on the hira (flat, above the shinogi) but most don't.
The Carter that Dave posted is pretty crazy. I've got two and their bevels aren't anywhere near as horrific. My Toshihiro actually was quite nice to flatten and thin; even from 800-grit, there were almost no wobbles or high/low spots. Though I like my Zakuri knives a lot...some of them have been quite a bear to achieve a nice flat even bevel on.
Carter:
Toshihiro (bottom knife):
Zakuri fresh (top knife):
Zakuri cleaned:
For the trouble that some of these cause...once the bevel has been flattened and thinned appropriately, they are some of the nicest knives out there. It's a shame more makers don't invest more time and effort in getting a consistent bevel (though it can be argued that it's not necessary as long as long as the edge itself is not affected).
