Hey Stephen,
I take it you're talkin' about those 2 you posted the pics of. The guys are right. You can, but you probably shouldn't on a treated Damascus blade.
It's not that hard with practice and Damascus isn't some super steel that you can't grind or work. The real problem is as Karl pointed out. If you file, sand or grind Damascus...the etch goes away. Then it pretty much just looks like any other steel.No pretty graining.
Besides, those are great looking classic designs. They are more commonly done without thumb grip filling than with anyway. Nobody's gonna hold it against ya! ;~)
Spend the extra time on fit and finish of the scales. That's what will be most noticed anyway. That's what separates the good makers from the great.
Just go to Karl's site and check out some of his work. Most of his knives are simple, understated, straight forward pieces. Unless you know enough about knife making to catch all the trick little stuff he is really doing. But you can see the quality in each one.
That's the kind of attention to every little detail of fit and finish that will stand out the most.