I think your definition of roleplaying is too narrow in the context of D&D.
Over the last week I took advantage of the excellent "Powerlevel Gary" thread and read through all of the Q&A threads that a kind poster linked in from the archives. Fairly regularly through threads lasting for the last 2+ years of his life, Gary expressed a certain derision for the notion of thespianism, improv theatre or play-acting as being part of roleplaying games.
I am usually uncomfortable making an argument based on an appeal to authority; but in the case of a publicy stated opinion of the original creator of D&D, I will do so.
Roleplaying was intended to be the assumption of a race and class and interacting with the world based on that choice of race and class.
There's an excellent series in Dragon, from about 2000 (ish) just after the release of 3e where Gary took a reader poll on what constituted the important elements of an RPG and then he discussed in his Up On a Soapbox column the results. He stated there that he was rather surprised that improv theater ranked number 1 or 2 (I misremember which) as the most important element in RPG's.
I'm thinking that perhaps the definition of RPG has evolved some since the mid-70's.
Ok, and I think that is bending over backward to find offense where there is none.
/snip
Not unlike the way some decided to take offense at every single word that came from WOTC's mouth in the run-up to 4e. Kinda annoying isn't it.
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Really, this is simply a genre discussion. Or close enough for government work. We can all likely define the far ends, it's just when one genre bumps up against another that things get... sticky.
For example, I think we'd all agree that 2001 A Space Odyssey is SF and LotR is Fantasy. But, there's a whole host of works in between those two points. Is Star Wars SF or Fantasy? Depends on who you ask (and don't think coming down on one side or the other of THAT fence won't start paroxysms of nerdrage. )
I think we'd all agree that if you're sitting at a table with Gary Gygax, a bunch of dice and OD&D books playing through his version of Greyhawk, you're playing D&D. OTOH, if you're sitting down with John Wik and a JENGA tower, you're probably not playing D&D.
The thing is, there's so much in between those two extremes. People talk about the differences between 3e and 4e. Yet, mechanically, 3e is miles closer to 4e than it is to OD&D (or Basic D&D for that matter). 1e and 2e are fairly close mechanically, but, to fans of either system, there are gigantic differences. And, stylistically, they've got a point - 1e was heavily influenced by pulps and S&S fiction, 2e draws much more heavily on epic fantasy traditions.
The trick is, people draw the lines based mostly on their own preference. "I don't like X, therefore X isn't something that I like". It's tautological. I don't like 4e, I like D&D, therefore 4e isn't D&D. And D&D fans have done this since AD&D was released. Just ask Diaglo.
How many people do you see who like an edition that claim that that edition isn't D&D? (and no, a single example does not disprove my point. This was meant to be rhetorical. sit down in the back there, you.... sigh.

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