Death and Dying
We’ve established that the average person in D&D has 3 hit points. They can take 3 points of damage before they collapse from their wounds, and they can supper a total of 13 damage (10 more than their HP) before their body gives up and they are dead. Up to -9 HP it is possible for them to stabilize and recover naturally.
According to the SRD, a character who is dying (fewer than 0hp) has a 10% chance per turn to naturally stabilize, or else they lose another hp. At this rate (and understanding a D&D Turn to be 10 minutes), most people will be dead within an hour and a half. Even if they stabilize naturally, unless they have someone to aid them they will lose hp every hour until he becomes conscious (again, 10% chance per hour), and even then he will not begin healing naturally for some time (10% chance per day, or lose hp). If there’s someone around to help, the character stops losing hp and start healing naturally as soon as they stabilize — pro tip: always travel with a group.
Having established that hit points are real measures of actual injury, this becomes a model for the body’s ability to repair itself; it is litterally a measure of how close your character is to death, whether he’s being pummelled or just bleeding out.
Natural healing in D&D 3.X is 1hp per day, per level — or 2hp per day per level if you get complete bed rest. Generally, any fight you can walk away from you can recover from in a day or two; this is partly because a hp is roughly 1/13th of a character’s vitality, and because an injury does not need to be completely-healed to be mechanically-irrelevant. Bruises, scratches, and the like are too small for the coarse-grained HP system to track, and day-old wounds appear to fall in the same category.
I have to admit that I’m surprised to read that an Nth-level character heals N times faster than other people; given three characters stabilized at -9hp, the 1st level character is on his feet in a week (6 days at 2hp/day), the 2nd level character is on his feet in a few days (3 days at 4hp/day), and the 3rd level character is on his feet in only a couple days (2 days at 6hp/day). One way to explain it would be to say that a higher level character recovers quicker even if he doesn’t actually heal quicker, but that undermine’s my intent of “1hp means 1hp, a wound is a wound,” and I’d probably scrap the idea in my own games — characters heal 1hp per day regardless of level. (As an aside, actually healing quicker makes sense for a evel 5+ character, and below that level it might be easy enough to handwave the difference.)
A major benefit of “hp is wounds,” in my opinion, is that it makes magical healing more reasonable. This is more important than the quirks of natural healing because it’s concievable that a higher-level character actually does heal quicker, but more particularly because in most games natural healing doesn’t come up. With access to Clerics and potions, most groups will take the time to refresh themselves to as close to full health as they can as often as they can. Asserting that “hp is wounds” normalizes magical healing, so that it affects people the same way regardless of Class or Level. A 1st Level Wizard and a 5th Level Fighter recieve the same, objective benefit from a potion of Cure Light Wounds, rather than having the Wizard’s sucking chest wound close up while the Fighter’s cuts and bruises just sting slightly less.
This also lets us talk objectively about the Cure spells and what they mean. Cure Light Wounds does 1d8+1 points of healing, about 5 on average. “Light” in this case is something of a misnomer, as 5hp is enough for most people to be dying. Cure Moderate Wounds does 2d8+3, or 12 on average. “Moderate” wounds are enough that most people would be on death’s door. Cure Serious Wounds does 3d8+5, 18 on average; Serious wounds put a trained fighter into his grave. Finally, Cure Critical Wounds does 4d8+7, or 44 on average. That’s more than three mortal wounds for regular people.
I think that wraps up the notion of hit points as actual wounds. By the book there are three factors to consider: how long you can fight (positive hit points), how long you can survive (negative hit points and death threshold), and how quickly you can recover (whether 1hp/day or 1hp/day/level). Regular people can sustain 12 and 14 damage, with trained soldiers weathering as much as 17. Higher level characters can fight longer and survive more serious wounds, and may recover from their injuries quicker. A few points of damage are enough to put someone out of the fight (it’s a coarse-grained system), and 10-13 points of damage can be considered a mortal wound. Scratches, superficial cuts and bruises, scars, and the like are too small to be tracked by hp, and the actual details of any given wound/attack are abstracted into the damage roll. If you know what the wound is (ie, slitting someone’s throat), the hp system probably isn’t appropriate.