We’ve already had that discussion in that thread awhile back, and everyone has said you are wrong. Vader was seething angry when he left Bespin. He didn’t have enough time to calm down, it was still the heat of the moment. If you have ever played a physical contact sport, you will know exactly what I am talking about. Luke had defied him, then hurt him with a lightsaber to the shoulder, and in a fit of rage Vader instantly chopped off the insolent kid’s hand. You can hear in James Earl Jones’s masterful voice performance, that Vader has to really hold himself back to not kill Luke. “Don’t make me destroy you” was of course a threat, but Vader’s temperament was so unstable with rage, he had to concentrate to hold himself back.

In contrast, by the time Vader reached the bridge of the Executor, he had time for “cooler heads to prevail”. He was no longer threatening Luke when they communicated with each other through the force; rather, he was pleading with him as any father would to his son. That difference in tone, the change in tactics from threatening to pleading, is what got a different response out of Luke. And the softer response out of Luke further softened Vader.

When the Falcon escaped into hyperspace, Vader’s emotional state was completely different than it was at the end of their duel.