>In 1e its not presented as optional rule in the DMG, but what is optional is how much you can be reduced to and not die (in one hit). From 0 to -3 is the default.
Are you referring to this section? Because I'm not at all clear on what he's saying. Like many of the bullshit complexities of AD&D, this is something that seems to always be ignored in actual play.
>Zero Hit Points:
>When any creature is brought to 0 hit points (optionally as low as -3 hit points if from the same blow which brought the total to 0), it is unconscious. In each of the next succeeding rounds 1 additional (negative) point will be lost until -10 is reached and the creature dies. Such loss and death are caused from bleeding, shock, convulsions, non-respiration, and similar causes. It ceases immediately on any round a friendly creature administers aid to the unconscious one. Aid consists of binding wounds, starting respiration, administering a draught (spirits, healing potion, etc.), or otherwise doing whatever is necessary to restore life.
>Any character brought to 0 (or fewer) hit points and then revived will remain in a coma far 1-6 turns. Thereafter, he or she must rest for a full week, minimum. He or she will be incapable of any activity other than that necessary to move slowly to a place of rest and eat and sleep when there. The character cannot attack, defend, cast spells, use magic devices, carry burdens, run, study, research, or do anything else. This is true even if cure spells and/or healing potions are given to him or her, although if a heal spell i s bestowed the prohibition no longer applies.
>If any creature reaches a state of -6 or greater negative points before being revived, this could indicate scarring or the loss of some member, if you so choose. For example, a character struck by a fireball and then treated when at -9 might have horrible scar tissue on exposed areas of flesh - hands, arms, neck, face.