That's great advice, and it pairs well with all the words of wisdom regarding not speaking or acting in anger.

Often people threaten in situations where they know they are powerless and cannot act, whether on a threat or anything else. When you have power and you know it, you act differently, more confidently, and as though you know nothing is lost by keeping the mouth shut until ready to act.

But your threats speak for you as well. They warn your opponent how and where you intend to strike them, should you ever be able to do so, and tell an observant enemy exactly how you think and what would frighten or piss you off, because that's what you're trying to do to them by threatening them.

Your entire appearance, tone of voice, and choice of words also tell an opponent a lot of the real truth about your immediate attitude and maturity level, and whether you're personally even worth changing their course to help.

Threats are a product of fear and anger, and are not nearly as threatening as the people making them think they are. If you want to threaten, act cool and confident. Laugh at them when they start getting flustered.

"Oh" and "heh, okay" are how to respond to threats being made to you, like they just don't matter and your real position is whatever pal, if it makes you feel better. This level of near-total non-response gives you time to evaluate the situation and do nothing you'll regret, or to do something later that you've planned out far better than making angry threats in the heat of the moment.

Threats are almost always the most stupid tactic there is. You're gonna call my boss and have my job? Not before I call him, lol. But thanks for letting me know. Have a nice day.

This is how threats telegraph weakness to people who are accustomed to holding power. If you want someone to know for sure you hold no cards, start whipping out threats.

TL;DR: Threats are best avoided until you are truly ready to act. And if you can't act, keep it shut until you can.