Indeed, I have seen that before. It can't really count as concrete proof, though, since that may have been Kirby's INTENTIONS, but one has to factor in all the countless other people who have worked on the character since then, none of whom has shown us his face. Until we actually SEE Doom's face in-comic - and personally, I don't believe we ever should - we can't tell whether he actually IS horribly scarred, or whether he and other people have been overreacting. (Hell, I wouldn't put it beyond Doom to give anyone who he's come in regular contact with a posthypnotic command, so that if they ever see his real face, they will recoil in horror, regardless of what it actually looks like. 'All of you will SHARE DOOM'S PAIN!')