We do really had choice. I wasn't active in thread then, so i am curious to know why people still chose to include this insight.
Sure, there were a couple of reasons that were bandied about, but here is a slightly more developed reason. After all, this idea has had more time to develop.
"The Mirror is clear, revealing all deceptions, including those of the self. Yet this is no matter of virtue or vice, only an understanding of the self. Whether following reason or passion, one must face forward and acknowledge the truth of their choices, without deception."
The core insight of the Argent mirror is to confront the world as it really is, to carve away deceptions of self and others and make decisions using that truth. The particular method of the decision doesn't matter, either reason or passion, but it makes us confront the deeper truths of why we make certain decisions, or why the world operates the way it does, without relying on comforting falsehoods and deceptions.
Ling Qi has had a habit of running away from insurmountable problems, of always being tempted to flee when it might give an advantage. Retreat is a tool that Ling Qi uses to gain advantages that could not be gained by standing her ground. However, this mindset also appears when confronting truths that she doesn't like. Ling Qi hurt her relationship with Meizhen because Ling Qi deceived herself and Meizhen regarding the possibility of Ling Qi returning the affection.
The insight gained from the Argent Mirror helps to avoid such self-deceptions. It compels one to force the truth of themselves and deal with that truth, no matter how ugly that truth might be. It tries to keep one honest with themselves which allows them to make more consistent decisions with their desires as well as capitalize on the truths that are hidden in the deception of the self.
It is a difficult insight because it denies the comfort of self-delusion. We see this in the "King of the Forest" arc where Ling Qi could not hide behind the delusion that she would have stood up to the King for her real friends. It reveals to Ling Qi the inconsistencies in her thinking and forces her to confront the truth that she might not have stood up to the King for her real friends. That she lacks conviction about who her real friends are and what that means. It provides no answers, but assists in the revelation of the areas that we are unsure about ourselves.
Now, this might not be the only argument for Argent Mirror, and it is certainly a controversial argument. There are many people who hate the argent mirror insight, and no amount of reasons will convince them otherwise. But for good or for ill, it is the insight that we have, and it has some good potential to assist Ling Qi.