The kydex is going to attract dirt and abrasives. Anything you contact-cement to the inside to deaden the sound and soften the touch on the blade is going to hold water, against the usually waterproof nature which I feel is the biggest draw of this type of material. I'd recommend putting a lengthwise hand-finish on your blades to minimize the appearance of inevitable scuffing. Be careful finishing the mouth of the sheath because any sandpaper grit that gets in there will scrape the blade and bolster/handle where the kydex grabs. You can with experience get the fit tuned so there's a very small "plick" sound as the knife snaps in and out instead of a big snap, a lot of this is also keeping your fasteners close to the mouth of the sheath so there's less resonance.