I ordered take-away food in the Meituan, ate it, and then refunded it on the grounds of physical discomfort. How did the merchant agree to give me a refund? What happened?

The merchant is afraid of trouble, because he is afraid that you will complain about him, and he will get more than one bargained for, and he can't guarantee that all his dishes are 100% good. So when you complain about your discomfort, they will choose to compromise. It is difficult to do business, so I can't help it. If you all meet people like you, you will lose money sooner or later.