
Ah the beauty of moral ambiguity!
No, I don't think I've seen a mod for this so far. But... wouldn't it just be easier to have some self control and simply not exploit it????
and then two posts later:
I don't see how you abused anything?
@DTH: indeed "self-control" would be a _possible_ but not nearly so fun solution as a mod

I like games that contrain me into 'realistic' or at least internally-consistent dynamics. Obviously TES are far from 'realistic' in the real life sense, but . . . being able to spray an NPC tutorial hand-holder with flames for an hour in total (as a way to 'train up' Destruction) and him NEVER having fought back, nor died, is not particularly internally consistent with how he behaves/reacts IMMEDIATELY after leaving Helgen Keep.
I'm guessing that certain NPCs in the game cannot ever be killed? Else, Rolof and Hodvar are set to be 'essential' and unkillable until after comletion of the first quest, and also set not to aggress player hostility. They WILL aggress, if you hit them with a Fury spell (or at least he did before I looted his dead buddy, so maybe that was just because the "Unbound" tutorial quest had not started yet?). So it must be something that could be readily turned "off."
Pretty obvious that Bethesda has it set up that way so that new players don't accidentally get friendly-fire aggro within 5 minutes of starting the game and get discouraged. Which is a totally valid reason for the dynamic to be coded in that way. But for experienced and wiley players like me it becomes a 'forbidden fruit' that is just too hard to resist . . .
In my opinion, a mod that simply made them fight back would be adequate. Even if they cannot be killed just fighting back when you harm them would be good.
But for now, I shall enjoy my prodigy altmer who has risen to the lofty heights of Level 7 / Destruction 40 before his first steps into SKYRIM!!
did you follow hadvar or ralof? i dont think many people know you can stop ralof early...once he cuts you loose and you fight your first imperials, quickly kill the captain and loot her before ralof does. she holds the key to the gate that ralof normally takes but if you have the key then he has to wait for you to open the gate, leaving him open to attack with your sword or flame spell and grind levels without him moving.
I have abused both Haggar and Rolof now

You can do it pretty much at any time during the tutorial, or at least after the tutorial mission starts and until you exit into Skyrim -> you can cause damage to either one of them, they will not fight back, and they wil not die = you can "train" various offensive skills on them as much as you want.
Haven't checked to see what the Fury does if you hit them with that after the tutorial mission gets past the first stages.
I hit Rolof with Fury pretty much right after he untied me but before I looted his buddy to initiate the next stage of the sequence, so this was in the very first room in Helgen, and before the Captain and Hodvar come from the other entry series. At that stage, if he is hit will Fury he WILL fight back and kill you.