If I, as DM, say "The stab wound in your thigh still pains you, and it will take a week of rest for it to heal, but you could press on if absolutely necessary", versus "The stab wound in your thigh still pains you, and it will take a week of rest for it to heal, but you could press on if absolutely necessary, taking a -5 penalty to speed and a -2 penalty to all attack rolls"... shouldn't the party who is concerned about 'realistic' healing times for injuries make the same decision in either case... whether it be 'press on' or 'rest'?
Thats the crux of it to me... Anytime I've ever been in immersive mode, and everyone is on the same page, the rules seem to matter less. If something seems invalid, even if allowed by the rules, players tend to just go with what would be more realistic. IE we rest until our wounds heal. Or we don't jump off a cliff even though we know it will never kill us, etc...
It's only when players and Dm aren't on the same page that problems arise.
Immersive DM: "Your wounds pain you, and you feel it will take a week to heal..."
Mechanics Player: "I'm at full HP, so who cares. I'm pressing on."
Immersive DM: "But your wounds aren't healed."
Mechanics Player: "Whatever..."
Imposing a mechanical penalty gives the immersive Dm some measure of control over that. To sort of force everyone, mechanical player or immersive, into his sandbox. (Whether you agree with it or not is another topic.)
Immersive DM: "Well then you take a -5 on your attacks until you heal."
Mechanics Player: "Damn... I guess I wait a week to heal up."
Raven, I still don't understand what the issue with the healing surge representing overall health is?
So it doesn't say thats the case in the book... 4e like all D&D versions leaves a lot open to interpretation. Which is the best part in my opinion. None of the versions have said anything about lasting wounds.
Using Healing Surges to track overall health is a way to allow both martial and magic healing without the weird how did his words close up my wounds issue.
I'd still admit you'd have trouble with it in your sandbox though because of the speed of their recovery. That's an easy fix though by just slowing the rate down. Yep, it's a house rule, but D&D has a long history of modifying to suit whatever page the players are on...