Did Mountain not notice his opponent always keeping his comrade behind him? Of course he did, and he had been only too happy to let it happen. One could only say that happiness and sorrow were from the same mold, two sides of the same coin.
Turning a two-on-one fight into a duel between the two of them was for the best, as the de facto strategy in a multi-person slugfest would always not be to try to beat everyone, but to concentrate on killing anyone close.
Mountain could only be happy when his opponent was spreading his focus to keep his companion protected away from his green eyes, forcing himself to always keep a position that sometimes left him open for pain and wounds.