1. I think, it's 50\50 situation. You can be a wise and very kind persone but your speech may sound awful, and people think that your another fool and prefer not listen you. But that's not true. It's the one side of situation.
2. If we look at the second quotation, we find another side. Sometimes, your speech can tell about you and your past more than it needs. So, we must be careful and speak correctly, and also clearly.
3. The third quotation is the hard one. I inetrpreted it as the less person talks about himself the less people know about him or his personal life.