recently got a samsung galaxy note 3, and well to be perfectly honest the touchwiz UI is a steaming pile of- you get the idea, looking around the internet there is some concern about knox status 0x01 being used to deny accidental damage repairs, but according to samsung its not intended to verify warranty status, merely the integrity of the devices SW.
now i could see a claim for a failed display/wifi/what have you being caused by modified firmware (possible but unlikely, I'd just eat the repair cost in that case) and any issue related to the software i am savvy enough to repair on my own, my primary concern is with say a smashed digitizer or water damage to the device covered under JUMP! being denied due to said software changes, when they have no bearing on a structural or environmental-based failure.