This is why your chosen definition for the term "metagaming" is meaningless.
You've just decided that a particular bit of knowledge that the player has must influence that player's character's actions.
Because if I explain the personality and attitude of my character and how that means he would do what I want him to do, it is "metagaming disguised as roleplaying" because you say I am choosing that action because I know what I know.
And if I, knowing what I know, choose a course of action for the character that is specifically not the above action - while I could have chosen the above action, had you not provided me some piece of information - then I am still "metagaming", unless your definition for the term isn't "using what I know, rather than what the character knows, to choose my character's actions." because I would not be avoiding that particular action if I didn't know what I know.