(For anyone not aware, this is related to my guide Making a Unique-Voiced Follower in Skyrim.)
I’m sorry. Firstly, for the length of time it took me to answer this question.
Secondly, for the nature of the answer: I simply don’t know. Karl Pilkington hasn’t got a facial scar so I never had the need to figure it out.
Hopefully the answers exist out there somewhere for you.