OK, Charles and I got into a bit of a discussion on the post about taxing 1% of experience points. Part of this is my fault, because although I've discussed my views of experience points and level here from time to time, I haven't tried to unify them all. But we do seem to have gotten into an impasse because Charles sees experience points as dissociated from anything in-game, and therefore any mechanics based on experience points *must* also be dissociated, even if the GM using them doesn't agree that experience points are dissociated.
So, must they be?
Obviously, experience points have a meta-game function of acting like a score. But does this mean that you are not allowed to associate that meta-game mechanic with something in-game?
In my case, I see experience points as reputation, earned partially from bragging about the monsters you've slain, but mostly from flashing around lots of treasure in town. This is why you don't earn experience points for treasure you don't bring back to town. It's also why you earn experience points for treasure in the first place. Level is, in turn, the confidence in your own abilities you gain from all the people talking about you as if you were the Big Cheese. You get a little bit better, just because you *think* you are a bad-ass.
I've slowly become more firm in that position.
First, it was just the difference in the way I handled level drain: you lose a level (confidence,) but not reputation (experience points,) so once you've "gotten back on the horse" (went on another adventure,) you can get your confidence back.
Then, it was explaining why you get an experience bonus or penalty for low or high ability scores: people in town find the supposed exploits of a scrawny fighter a little harder to believe than a burly fighter's exploits, so you have to work harder. This made me long for the return of the secondary and tertiary experience adjustments, which fell by the wayside very early: you used to get a smaller boost as a Fighter if you had a high Intelligence and Wisdom, too.
Then, I started speculating about adjusting earned experience downwards if you don't have any proof of beating a monster. There's a chance that you won't earn experience, unless there's proof, and your Charisma can affect your chances of convincing townies. I even threw in a chance to get half XP for monsters you *pretend* to slay. This led, naturally, to bards draining levels through satire, to reflect a loss of reputation.
It all falls apart if you don't accept the idea of experience points as reputation, of course. If you treat XP as just a score, or if you interpret them as actual learned knowledge, my interpretation won't work for you. But I think under my interpretation, experience points *are* an associated mechanic; they *do* represent something in the game world, and the local authorities could charge you higher taxes because they think you have more money take.