I noticed it myself when I was trying to add a DRM-free title I just bought, Bone Dance by Emma Bull, to my Calibre library. Things just got a little harder for folks who like to store their Amazon purchases in Calibre. So, there may no longer be any need to use these workarounds. Update, 4/5/18: I just noticed a post in a MobileRead thread indicating that there are now Calibre plug-ins available for handling KFX.
