At the wedding, Flora Miller claws some lovely deep scratches onto Lord St Simon's face. By the time St Simon subsequently visits Holmes, they've vanished without trace.
Agnes Northcote's facial disfigurement switches from the left side of her face, when first revealed. to the right side when she is sitting while Holmes is telling her that he envies her for having a worthwhile opponent. She just remains positioned so that only her "unscarred" left side can be seen.