Hit Point Enigma

What is a Hit Point?

...being the number of points of damage the character could sustain
before death. Whether sustaining accumulative hits will otherwise affect a character
is left to the discretion of the referee.

The explanation above is from vol I of the White Box titled Men & Magic and it leaves a lot up to the players so far as explanation goes. So what do these "points of damage" entail? If a PC with 28 hit points takes 2 points of damage from a dagger, what has happened? Obviously White Box is a game and it's a game mechanic, nothing more. That doesn't help the story that is developing at the table or add to verisimilitude. For decades players have sought to explain hit points as something other than a game mechanic.
Abstraction is a part of any game. The problem with abstractions are that not everyone sees them the same. It takes a bit of work to adequately explain the abstraction inherent in hit points. The explanation I currently favor is that they represent everything from wounds to luck and skill at avoiding being injured. Damage reduces hit points which as a referee I may describe as getting one's shield between the blow and your body deflecting the worst effects, but lowering your ability to continue to do this. Or you just used up some precious limited luck, or drawing on your experience and training you turn slightly at the last moment taking the worst of the blow on your armor, but wearing you down. Eventually your pool of luck plays out, fatigue hinders skill and small bruises and scrapes add up. Can you still fight and cast spells, yes, are you closer to death? In a way the answer is yes, because your resources are nearing the end, but the real damaging blow, the severe wound that could kill has not happened yet.
So when does PC death occur? At 0 hit points? At 1 HP you are fine, at 0, dead? That is one way to play it, but the above quote from vol I gives the referee some discretion I believe. One way to play is at 0 HP the PC falls to the ground, spent, the accumulated fatigue, small injuries and stress has rendered him/her helpless, maybe even unconscious. Many referees play that death occurs at a certain negative number, say minus 10 HP. Until that is reached the PC is either bleeding out or dying or just unconscious. A negative damage equal to Constitution score is sometimes used in a similar way to determine PC death. The referee may set a number of rounds until death occurs during which stabilization or healing is possible, i.e. the death count-down. Some use level as the number of turns until actual death occurs. Some of these ideas appear in later editions and in other systems as official rules.
The concept of being bloodied once a PC, NPC or monster reaches 1/2 HP or less is used in 4th Edition and I think has some merit as a house rule for other editions. As I interpret it, bloodied does not imply a gushing wound, but rather the visible presence of their own blood on the injured. They have sustained visible damage that is a rough estimate of how far along the path to defeat they are and which may kick in additional effects at the referee's pleasure. A possible result of reaching 1/2 HP might be reduced combat effectiveness, or reduced movement whatever is agreed upon before play. It could also trigger an ability in either the bleeder or the opponent as it frequently does in 4th Edition.
However the referee treats HP, natural healing should be consistent with the model and support verisimilitude. PCs who reach 0 HP should heal more slowly than those who have not been taken so low if HP represents mostly luck, fatigue and other easily recovered resources. The very slow rate of natural recovery, 1 HP every day of rest after the first according to vol III The Underworld & Wilderness Adventures, seems to suggest that lost HP are actual wounds. Vol III does say "common wounds" when referring to the healing rate. Suppose "wounds" only occur when PC HP reaches negative numbers. Then healing occurs at the slow rate. Otherwise it occurs much faster in PCs who have not reached 0 HP and therefore suffered no real "wounds". Another interpretation is that healing of even small wounds takes a long time and the rate of 1 HP per day of rest is just what it is.
Fortunately the referee has great leeway in how HP and wounding is treated in the campaign. Perhaps no other area of the game is as heavily house ruled as the subject of Hit Points, with the probable exception of character generation...what referee really rolls the ability scores for their players?