I'm really not getting what the point of your posting here was if you refuse to engage anyone who disagrees with you. Just saying "Well that's your opinion" to every challenge is a complete dodge.
Have I been really saying that? Mostly, I've just put this up to invite discussion. I've never said "hey, you're wrong". I can take people disagreeing with me.
At least we agree that your statements were illogical. That sort of begs the question though: what were you expecting?
No, I think when someone says "you say XP should be rewarded for all actions, so I should get XP when I sneeze" is definitely taking my agrument to it's illogical conclusion. Now, if they had put up some other argument (should XP be rewarded for low-level "threats"? should XP be rewarded for smart actions that go against the genre of the game - such as building a cannon in D&D?), I'd be more willing to agree.
Nonsense. "on-the-fly negotiation with NPCs, the gathering of information ..., or exploration of the dungeon" are all possibly Skill Challenges and certainly all necessary for completing a quest (and thus for earning the Quest XP). Just because they aren't as directly rewarded as combat doesn't mean they aren't rewarded.
And here we go back into 4e again. I believe I mentioned that this wasn't an attack on 4e, that I was only using it as an example. I'm speaking in generalities, and you're speaking in specifics. Was NPC interaction rewarded in the R.A.W. in 3e? Not really. It has better representation in 4e (I believe I've said this already), but it's still not perfect. You obviously feel differently. I can accept that.
Not very satisfactorily though. Almost all of your "Bads" will keep following you to whatever system you switch to until you correctly diagnose and address them.
Actually, I do address them. And they're not all entirely "bad". This post was not a personal complaint - I'm sorry if you feel that it seems that way. It's instead just an observation on how RPGs are designed.
Think of it this way - if you were going to try and turn 4e (or 3e, or 2e... I don't really want to get edition-specific) into a mystery/horror game, what would get in the way of that? From one of my "bads", I'd argue that part of it is due to that acting in a manner appropriate for a horror/mystery game is not rewarded by the RAW of D&D editions. I'd suggest you'd need to rewrite the XP awards to better fit your genre.
Also, the "level up in the middle of the adventure" has been a problem of mine in the past, and I've seen it while sitting at other tables, too. In my campaign, I'm the only guy with the books (this isn't that unusual, is it?) - meaning the players HAVE to level up at my place, which cuts away from gaming time. The only fix I have for that was getting more PHBs at the table, and doing whatever I could to speed things up.
As for my "Some settings are not served by XPs", that's a vague example. I'll give you that, but I can think of a few settings where XPs just feel
off in the game. Personal taste there, and that's a hard thing to argue against (I'm sure someone will try, though.

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I disagree that it is discouraged, but even if you want to reward it more for some reason, I think the "best fix" is rewarding XP for good RP, not getting rid of XP. It's so central to D&D that if you really have that big a problem with it you should probably just play a different game. Playing D&D without some sort of leveling mechanism is like playing Monopoly without the ability to buy property.
Like I've said elsewhere,
I don't really have a problem with XP in D&D. And, as I've also said,
This thread is not about D&D specifically, but XP-based RPGs in general. Maybe I should have stated that more clearly in the original post, but I thought I made that obvious.
I agree that RPGs need some sort of improvement mechanism, but I don't think XPs are the only way this can be done. I can think of a few examples -
* Chaosium games have a system where each skill you use has a chance to improve. At the end of each session, any skill you use has a chance of improving by an improvement roll (my game, by the way, does something similar, except that your skills improve during actual play).
* The original Gamma World had no levelling mechanic - PCs improved only through the gear they received, and through mutations they may acquire during play.
* Savage Worlds, while an XP system, had "bennies" that were essentially action points. In the original system, if you kept any bennies, they could be cashed in for more "xp". The neat thing about them was, you could get more bennies (basically awarded at the GM's whim, for doing something in the spirit of the game).
I'm sure people with more RPG knowledge can think of others, but games without XP are hard to find. I'm sure that's because XP work fairly well (I'd agree with that). I just think that there are pitfalls to that assumption, and I gave them in my OP.