AbdulAlhazred
Legend
Yeah, I spotted your post about role in original D&D, I think that was a fair analysis of what Gygax meant. 'Role Play' was, AFAIK, not a term at the time, though certainly 'playing a role' in the sense of 'being an actor and depicting a specific character' would be a potential interpretation of that phrase. Still, I believe you are correct in diagnosing that Gygax is discussing the role a given PC plays within the adventure, and not talking about players in some other sense separate from the character.@AbdulAlhazred
No disagreement on the trajectory.
But (i) I don't think that that sort of character development is what is being referred to as "role" in Men & Magic or in Gygax's PHB. Both present role in terms of class, and alignment, and to a lesser extent race. The elaborately-developed character is more of a by-product, or an emergent result, of the underlying features of the game we've discussed in this thread: (a) the game takes place in imagination, with imagination (constrained, obviously, by situation and by role) as the limit on what can happen; and (b) players engaging the shared fiction by declaring actions for a particular character who is "theirs".
And (ii) I think that there is a significant degree of system-level collision between some of the core game processes, and that emergent orientation towards character. The XP rules are probably the most obvious, and it's no great shock that the original OA had to tweak them in various ways, and that 2nd ed AD&D changed them wholesale. The action resolution rules are another, as they are not all that robust once the situation moves beyond the core focus of dungeon crawling: 2nd ed AD&D just punts on this, while 3E, 4e and 5e D&D all respond in various ways.
The struggle over (ii) - manifested in everything from Why does V:tM, or even Traveller for that matter, need elaborate combat rules?, to the declining proportion of D&D rulebook real estate devoted to doors over the editions, through to the invention of non-map-and-key techniques for presenting situations, and the various sorts of approaches that now exist to social conflict resolution - can be seen as defining much of the history and direction of RPG development over the past four to five decades.
D&D certainly didn't require, nor even especially actively promote RP in the modern sense. It could be motivated within the rules you cited which discuss things like the proper time to 'give full XP', but even there Gygax seems to mostly be concerned with substantive actions and not characterization. However I think that's a blurry line in many cases, so a player acting out being a leader when playing the Fighting Man, for instance, kind of falls in both kinds of 'role'.
I do think there's a trajectory though, and the emergence of 2e's XP system, as well as OA, indicates that sometime after 1979 or so that the idea of role playing as a thing in and of itself became more and more important to game designers at TSR. Certainly when OA (1985 IIRC) was published it seemed to lean in that direction. While you pass off 2e as not addressing task resolution, it does do SOMETHING, NWPs are there, granting they're not the greatest mechanical implementation of a skill system. OA and DSG/WSG also had them, so the idea was there (and even the original PHB had to talk about secondary skills).
There are other signs too, thieves get more abilities, and the right to decide which ones are important to them. So you can be a pick pocket, or a wall-climber, or a trapsmith, or a bit of all three (the totals actually sum to the same numbers as 1e thieves). The much-maligned UA thief/acrobat class similarly points to a desire to broaden the action resolution system. I think TSR simply was reluctant to really break with existing D&D in a more substantive way. Given the violent reaction to 4e I'm not sure I blame them!