“We dismiss genuine appreciation from a known quarter. And genuine feedback from a stranger ” — May be because we think that the person knows us and might be biased towards us, whereas for unknown strangers to shower praises or criticize: he has nothing to gain or loose hence it tends(not every time) to be more genuine.
I think more than person/quarter (loved ones or strangers) its more of how we feel about the authenticity of the feedback. I think it comes from experience.
A mother would always appreciate you no matter what, however it becomes so common for us, that even when she is genuinely appreciating you, you feel that you ignore her appreciation.
Eventually its your own experience that adds up to all of this. The moral is not to forget those events or scenarios where you were given feedback and analyze later which were the genuine ones 🙂