World XI captain Smith advised players not to tell tales out of school after the first day of the Super Test at the SCG, during which he has Andrew Flintoff - who, according to Vaughan, he branded a "big baby" throughout last winter's tour of South Africa - and Steve Harmison under his charge.
There was plenty of animosity in England's 2-1 Test series success in South Africa and Vaughan revealed Smith called him "queer" on a regular basis.
The relationship was not helped when, during a fourth Test hearing into comments by Vaughan relating to the consistency of the umpires' decisions on bad light, Smith stood as a witness.
Smith, who detailed the sledging he received from the Australians on his debut in a magazine article three years ago, said: "It is sad when you take things that happen on the field off the field. You sometimes say things you regret.
"Sometimes things get said and done out in the middle. We are all playing for our countries and it is tough.
"Once you get to know one another you get on well, it is hard to judge people just on a cricket field.
"I was naive maybe talking about the Australians as a young guy. If I could have that time back I would not do the same thing. It's private what happens on the cricket field."
In the middle, Smith's international all-stars were aided by the new umpire referral system which appears to have removed the benefit of the doubt for batsmen from the decision-making process as Michael Clarke was given out caught at silly mid-off and Shane Watson was adjudged leg before as Australia finished on 331 for six.
But centurion Matthew Hayden escaped via the same type of conference between the on-field umpires and third official Darrell Hair when, on 28, he shouldered arms to spark a confident lbw shout from Harmison in the first over after lunch.
"It is not good for the heart but it has worked because they have made the right decisions," said Smith.
"Some look out with the naked eye and some don't and so I think it is going to work out evenly either way."
Hayden clung onto his Test place by virtue of his hundred in the Ashes decider at The Oval last month and followed up with a 22nd three-figure contribution in similarly subdued fashion.
It appears his days of bullying attacks are on hold for now with the new tempo proving successful.
"I was really disappointed coming off that Ashes series," Hayden said. "My batting strategy in the first three Tests was not as I liked, by the fourth I had lost a bit of confidence but in the fifth I had a good strategy, was patient and looked to build an innings over a period of time.
"You can only bat as a well as they bowl and it takes a really good attack to make you disciplined.
"Both the English attack and this one we are facing here are high quality with good skills and patience and it has taken an extraordinary approach to counter-act that. "This has been one of the most difficult periods, not just for me but all our batsmen, for a number of years.
"The way I look at it I have got a choice, I am not going to hoodwink myself: if the bowling is off I will be looking to be aggressive, if the bowling is on there is no point in going hard because it doesn't work."
With Harmison and Flintoff the only mainstream seamers chosen for the contest, after Shaun Pollock was left out, Vaughan might have further reason for grievance with the tour of Pakistan a fortnight away.
There will be plenty more work for them to do with the ball in the contest, it would seem, in support to spinners Muttiah Muralitharan and Daniel Vettori.
"It is a gamble going the way we did but we relied on our two spinners and two seamers with Jacques Kallis as back-up," Smith added.
"Hopefully it will reap bonuses later in the game if we bat well."