That is literally a definition of role-playing: You abandon your own perspective, and instead think like the character.
This is ridiculous. Playing a role does not require abandoning your own perspective, as it inherently entails playing that role from the point of your perspective. You may be attempting to guess what the perspective of that fictional character may be, but you are doing so from your own perspective and play goals.
The role does not exactly have some sort of objective reality in itself. If you asked multiple people who shared your own dogmatically-bound perspective on roleplaying to roleplay a given character to the backstory you all agreed upon, then the character would likely still be played differently because the players' perspective on how the role should be played will differ.
In fact, I would argue that the definition of "role-playing" as a term literally entails meta-gaming as part and parcel of the process. A "role" is a meta-textual construction that only has meaning outside of the fiction for the participants, while "playing" entails an inherent awareness of the recreational purpose that drives the participation in the process. Likewise, "role-playing" as a process involves the player playing an imagined role that exists in distinction from the player themselves and that one cannot actually assume the role of a fictional role without bringing one's own cognition and perspective to bear. The player will be aware - assuming here that they are not sociopaths - that the game is being played with a recreational purpose, a tacit social contract (of some sort or another, likely including at the least not being a wang-rod to other participants at the table), and an attempt to making sure the actions of the character in the fiction do not disrupt play in a manner for other players in a manner that would disrupt their own desires for recreational enjoyment.
But let us also consider something else here for a second. Let's take the sense of "metagaming" from the wikipedia article on the same name:
Metagame, or
game about the game, is any approach to a
game that transcends or operates outside of the prescribed rules of the game, uses external factors to affect the game, or goes beyond the supposed limits or environment set by the game.
If we apply this to what Saelorn is advocating, then it becomes fairly clear that Saelorn's "definition" isn't so much what roleplaying is about, but, rather, the metagame that he seeks to impose on the roleplaying process. In effect, Saelorn is just wanting people to play by his metagame rather than the range of other metagames that others may use for approaching roleplaying.
Sometimes, there are situations where meta-gaming is the lesser of two evils, but it's never good. It's always to the detriment of the role-playing process.
You're free to not like the truth, or to find it distasteful, but that doesn't make it any less true.
If you disagree, then make some sort of logical argument to support your claim, rather than Appealing to Authority.
You're appealing to non-existent definitions that have not been agreed upon and that you have not sourced and treating these definitions as an authority. You're appealing to truth statements that have not been verified. You're making highly-charged, unsubstantiated ethical claims about these things. I don't think that you realize how hypocritical and hollow that your argument sounds when you use the sort of language that you are choosing to use here, Saelorn.
WHERE ARE YOU GETTING THESE DEFINITIONS?????
His preferred metagame.