In Chinese culture, maintaining social harmony (和谐, héxié) and giving others “face” (面子, miànzi) are paramount. Being 多嘴 is a direct violation of these principles. It's seen as a disruptive behavior that can create conflict, cause embarrassment, and damage relationships. While in Western cultures, being a “busybody” or having a “big mouth” is also viewed negatively, the criticism in a Chinese context is often deeper. It's not just about being annoying; it's about failing to understand one's proper place in a situation. The cultural expectation is often to “mind your own business” (管好你自己的事, guǎn hǎo nǐ zìjǐ de shì) unless your input is explicitly requested or required by your role (e.g., as a parent or a direct superior). A person who is 多嘴 demonstrates a lack of social awareness and respect for the personal boundaries of others, which is a more significant social flaw than simply being talkative.
多嘴 is a very common, informal term used in everyday life. Its connotation is always negative, but the severity can vary.