My issue with kydex sheaths has not been scratches on blades (scratches happen from general use anyway), but premature dulling of the cutting edge from scraping/rubbing on the kydex when being drawn or sheathed. I don't like to have to sharpen a knife more often than necessary.
I have a WIP for a Kabar Mk2 sheath using a leather welt sandwiched between layers of kydex. It would be a finish project if my pop rivet riveter had not decided to take a permanent siesta. (Yes I use pop rivets... when you are a frugal Texas farm boy and you have thousands of them laying around in boxes, you find uses for them

)