In the Bible, foolishness is most often an ethical concept and goes beyond a lack of native intelligence. Although the fool might be one who acts boorishly, naively, or imprudently (e.g., Prov. 10:23; 20:3; cf. 21:20), he is more particularly one who lacks the wisdom which comes with the knowledge of God, someone who in his pride is wise in his own eyes but acts contrary to the will of God and thus does (intentionally or not) what is evil.
Myers, A. C. (1987). The Eerdmans Bible Dictionary (390).
The opening verse sets the stage for the entire chapter and separates the masses. Stupidity is known by her stuborness. A refusal to change for the better is a clear sign of lacking good sense. Those who, by contrast, take note of their error show love for knowledge and discipline.
Prov 12:4 shows the power that relationships have over us. Our positive influence on others (the husband to the wife) reflects favorably on us, whereas contempt for others spoils intimacy in relationships (the wife to the husband). This is no dig on women/wives merely because they are used negatively, while the husband gets all the glory for the good behavior of his wife. The husband/wife relationship is used to illustrate that the most intimate of relationships can be affected positively or negatively by its members.
Again, our speech is called out on multiple occasions. What we do with our words and how they are used matters. Words can be full of redemption (12:6; 13); prosperity (12:14), truth (12:17), healing (12:18); permanence (12:19); blessing (12:22); kindness (12:25). The opposite is equally true.
Speaking of discussion, a fool entertains only monologue, listening to their own voice and giving no credence to the content of others. Soliloquy is their lot. The wise engage in dialog, listening to other voices because they know their voice is not the sole means of prudence. Community is their blessing (Prov 12:15).