For a character used to normal vision, fighting when blind is
obviously much more difficult than fighting when they can see
adequately. This skill reduces the challenge somewhat, making it
a little easier to do damage.
This skill is very similar to Second Weapon. To use Blind Fighting, multiply the character's skill level by the applicable combat skill level (ie. the weapon they are trying to use), and divide by 100. The resulting number is the character's effective skill level with that particular weapon while blinded.
Julia has a skill level of 62 in Blind Fighting, and a skill level of 74 in Martial Arts. If she is fighting in the dark, her effective Martial Arts skill level will be 45(=62*74/100).
To use this skill in conjunction with Second Weapon (using two weapons while blinded), simply apply one skill and then the other (the order doesn't matter).
For characters who are normally blind, there may be different circumstances.
For any character who is only temporarily blind (whether the blindness is due to a blindfold, complete darkness, intense light, or any other reason), this skill will apply, at default levels if the character doesn't know the skill.