I agree with him. His commenters saying that adding a complicated sub-system for tracking fatigue points is undesirable though, and I agree with them too. What we want is to keep the game simple and streamlined, and provide an option for anyone who wants to include some sort of rule for character fatigue or decreased fighting effectiveness due to wounds etc. in the game.
Here's what I'm proposing:
Combat Fatigue, Weakness and Wounds
A character or monster can not cause more damage from a physical attack than its own hit point value.
Example1: A wounded fighter with 3 hit points rolls a d8 for damage with their long sword. They also get a +1 bonus on damage for their high Strength attribute. However due to their hit points being 3 any value higher than that is counted as a 3.
Example2: A kobold charges the Wizard with it's spear. It rolls a d6 for damage but it only has 4 hit points so it can inflict a maximum of 4 damage against the Wizard.
This system has no additional points to track while representing a limited amount of 'combat fatigue', 'wounds' and weakness / inexperience. When character are at higher levels or not at low hit points the system fades into the background. It applies to both players and monsters and reduces some of the 'swingy' nature of combat making fights with weaker monsters easier to apply tactics to at lower levels.
It also changes some of the basic D&D combat tactics. Instead of ganging up on Orcs one at a time to remove them from combat (good D&D tactic, bad combat emulation) the party would alternately be wise to reduce all the orcs to low damage output by spreading their attacks around.
Let me know what you think. I thought of this on my walk to work this morning and haven't had a chance to try this in a game. :)