That's really the concept in a nutshell as I understand it: interacting with the game mechanics outside of the abilities of your avatar. Metagame. Not associated with things that the character controls in the fiction.
It can be a Big Deal for folks.
All RPGs involve this. From the obvious but inevitabel (eg writng and reading things, rolling dice, etc) to mechanical aspects like rolling for initiative (what is my character doing that corresponds to that?). I don't care where any particular person's cut-off is; I care about the projection of one peson's preferences or inclinations onto others (especially me!).
The reason for this (and this is my personal reasoning) is that the issue with spell effectiveness is far less intrusive.
I'm one of those who find the healing spells, and their labels, nonsensical. I think the same is probably true for many of those who migrated from classic D&D mechanics to systems like Runequest and Rolemaster. Proportionate healing is one of the features of 4e that made it attractive to me.
people get to not like things for any reason they care to dream up
Sure, I don't disagree with that. My complaint is when a person's dislike then gets projected from the first person to the second or third person, so they start saying that my game is not really an RPG, or that so-called "dissociated" mechanics are an obstacle to immersion in general, etc. (The latter is particularly common, and I know from my own table experience that it is not true in general.)
So 4E rules prescribe what the player can do?
And 5E rules describe what the character can do or what is happening to the character?
There is something to this, but I'd put it slightly differently.
All RPG rules tell the players what they can and can't do - eg they contain procedures for writing numbers on a PC sheet, and changing those numbers; they contain rules that tell the various participants under what conditions they can introduce new content into the fiction, etc. (For instance - in 3E combat, on someone else's turn you can't introduce new information about what your PC is doing except under certain special circumstances, or if the information is simply that your PC is saying something.)
The rules can try and make it so that every time a player makes a move according to the rules, it corresponds to something that is happening to the PC. The challenge is precisifying this in such a way that relevant distinctions are drawn. For instance, practically every time a player in 4e declares a power-use, his/her PC is doing something related in the fiction (some lazy warlord builds might be exceptions to this).
The precisification probably invovles something about the
scope of what it is that the PC is doing (eg Come and Get It: "I draw in my foes" is something that the PC is doing, but many players seem to find that objectionable as an action declaration). [MENTION=205]TwoSix[/MENTION] made this point upthread with his reference to PC fingertips.
Your ability to attempt to do this is unimpeded - you can attempt to fight off all of the goblins with 2 hit points or 200 hit points; that you're allowed to try is what's fundamental here.
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These are poor examples - in both of them you can attempt to jump the gap or pray for divine intervention; it's just that you have little hope of success. You're not disallowed from even trying, which is the key.
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There's a difference between being allowed to try something, even when the odds of success are nil, and being disallowed from making the attempt at all. One puts the agency in the hands of the PCs, and lets them succeed or fail on their own accord, even if failure is guaranteed. The other removes the agency to even make the attempt in the first place - there's no question of success or failure if you can't try.
the issue of "character resources" as dissociated isn't so much an issue of them knowing about it or accessing it, as them wanting to be able to do something and finding out that they can't due to metagame reasons.
I am really having a lot of trouble with this.
My fighter PC prays for divine intervention, and the GM tells me that I receive no answer. The GM's reason for doing this is that I'm not a cleric, and the rules say only clerics can wield divine magic. Isn't that a metagame reason.
Or, I declare my PC's attack against an adjacent goblin with my bow - but the goblin gets an OA, so attack first, and hits, and kills me because my PC had only 2 hp left. So my action declaration fails. That's a metagame reason - the reason I died was because of the action economy, which is metagame (the fact that the goblin is
always quikcer than my archery is not some inherent property of the gameworld), and because I had only 2 hp left, which is metagame. (In the fiction, how was I different at 2 hp from when I had 10 hp?)
Of course narrative material can be introduced to support all these outcomes, but that is equally true for an encounter power.
And of course the player of a character with encounter powers is free to have his/her PC try whatever s/he wants. It's just that the attempt is likely to be unsuccessful (subject to stunting considerations of the sort that TwoSix and others have mentioned).