I couldn't XP you again yet, so opted to QFT instead.Depends.
I've certainly had NPCs in my game who have suffered injuries - blinding, maiming etc - that the PCs can't heal just with a Healing or Inspiring Word. (I assume that Remove Affliction will heal this sort of injury.)While I have no problems with how players choose to envision damage in 4e. I personally take the more realistic approach to combat where surges don't close wounds at all.
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I'd rather allow my fantasy world to have people with lasting injuries with them. Though I've yet to impose such things on the PC's, I like to set the precedence that ones ability to heal isn't an immediate cop out for all injuries.
If even the smallest fraction of hit points is physical damage (which I believe everyone agrees on) then the fact that HS can bring one back from zero or less would seem to indicate that they can heal actual physical damage when applied in certain circumstances.
OTHER
There are no Wounds in D&D as defined in the rules. Damage causes whatever the DM wishes to describe it narratively. As such, healing is treated the same way. How it occurs is within the narrative control of the DM. One unified mechanic, Healing Surges, is used to cover a multitude of methods.
A Cleric's Healing Word may close wounds.
A Warlord's Inspiring Word may give the character the resolve to continue despite the pain he is in.
Since the earliest days of the game hit points have been described as a combination of physical toughness, skill, luck, resolve, etc. How those hit points are lost or gained have always been up to the DM to determine.