Great Old One
Imagining you are someone else and pretending to be that character? I imagine I'm Bob the Blue Wizard. I cannot cast spells, Bob can. I don't have hitpoints, Bob does. So, if I say Bob casts a spell, then I'm pretending my character, Bob, can actually cast spells. This requires nothing more than this -- I don't have to give Bob a backstory, or a motivation, or anything else, because I've met the requirements of this clause simply by agreeing that my character is a wizard.
Bob might be technically a character, but he is not "someone else" (... "imagining that you are someone else..."). Someone else is a person. Bob is not a person. And again, take normal actors, and Bob will not fit the bill by a long shot.
And yet you've focused quite a lot on that word. Your further expansions don't work very well, either.
No, you were the one who focussed on it, to the point that it seems that the only actor that matters to you is OW, the shining example of what being an actor means. sigh And that is, once more, because you are ruleslawyering a single paragraph, dissecting it to make every single word mean something very specific, like "actor = Owen Wilson".
I have. For a long time. Roleplaying according to that passage is fully satisfied by both cases of Bob the Blue Wizard I put forth above. If you don't smuggling in assumptions, that is.
Let's assume that, in good faith, the author actually meant what you claim. Then loads and loads of people played the game wrongly
No, they did not. Because, once more, you are the one putting a judgement of valor here. I'm not. Maybe some portions of the world at large was not ready for the concept. Maybe it was not a fun concept for some people at the time. Maybe the local culture and the way to play war/board games influenced people. As long as it was fun for them, it was not wrong.
But I went to a convention in France in I think 1980 or 1981, and you got points for technical objectives and for roleplaying your character, both. I still have the trophy somewhere in my basement.
And again, it's not a question of criticism of anyone, the question here is "did roleplaying change", it just goes to show that no, it did not, not significantly.
, entirely tournaments - put on by the people that made the game - were played incorrected, and the most recent edition (5e) had decided to break with this concept completely and allow for roleplaying that doesn't require what you claim.
And once more, I've shown to you that only a very narrow minded reading of one sentence out of all the 5e sections that speak about it allow this interpretation, as well as forgetting all the next sentences, which read: "In this case, it’s you as a player determining how your character thinks, acts, and talks. Roleplaying is a part of every aspect of the game, and it comes to the fore during social interactions. Your character’s quirks, mannerisms, and personality influence how interactions resolve."
Or "Characters are defined by much more than their race and class. They’re individuals with their own stories, interests, connections, and capabilities beyond those that class and race define."
Or the whole section on Personality Traits ("Give your character two personality traits...")
This last is a point that you continue to ignore and not address -- that 5e explicitly allows for Case 1 of Bob the Blue Wizard.
If you mean by "allow", 5e allows anything. But Bob certainly does not pass all the criterions above, and in particular no stories, no interests, no connections, no personality traits, etc.
And again, it's not a judgement of valor on Bob or on its players. But factually, he does not meet the criteria for a roleplaying character.
And yes, all the above also goes to show that, from a single paragraph in BECMI, we now have multiple sections of the game which give recommendations and even propose rules about generating and playing a role, in the roleplaying sense (and not as in "I'm the wizard of the party, I'm a controller/damage dealer"). The game has indeed evolved, the terms have changed (probably to avoid people continue to nitpick on Owen Wilson), but has not changed the basic way of roleplaying.