De Kock did not contest the charge at a hearing on Wednesday evening, though he aimed to lessen the sanction that applies to a Level 1 offence. Although he was unsuccessful in the endeavour and admitted he had said "something" to Warner, the South Africa wicketkeeper maintained he was not the instigator.
CCTV footage of the passageway leading to the dressing rooms showed David Warner being physically restrained and shouting at de Kock, who did not respond. Warner was charged with a Level 2 offence on Tuesday evening, and fined 75% of his match fee. Though he has accepted those sanctions, Australia claim Warner was responding to a jibe from de Kock, and they say it was "personal."
South Africa, however, have denied de Kock provoked Warner in any way. "We are appealing Level 1 because we think Quinny didn't do anything," the head coach Ottis Gibson said. "Quinny wasn't aggressive. You saw some footage, and the footage showed Quinny walking up the stairs and somebody else being restrained, and then Quinny gets a Level 1. That doesn't seem fair."
Gibson would not comment on whether de Kock was entirely silent, and neither would several team sources, only for the man himself to admitt he had answered back.
"Quinny would not have said anything had something not been said to him in the first place. But I wasn't out there. Faf was there. Faf probably knows what was said," Gibson said. "But there's one guy walking up the stairs going back to his dressing room, there's another guy having to be restrained. If I am walking, trying to get back to my dressing room and somebody is being restrained, how can you fine me for something?"
Asked if de Kock said anything about Warner's wife, which is what Australia are alleging, Gibson chose to focus on the undefined line and called for clarity. "I wasn't there. I can't categorically speak for another person. There's this thing and I have seen it recently now about the line. They are saying they didn't cross the line, but where is the line, who sets the line, where did the line come from? When you are saying you didn't cross the line but we didn't cross the line, you went very close to the line whose line is it?"
Chirping needs to stay on the field - du Plessis
South Africa's captain discusses the stairwell incident between David Warner and Quinton de Kock at Kingsmead
South Africa would really like the umpires to start answering that question. Du Plessis called for them to step in immediately after the end of the first Test. But Kumar Dharmasena and S Ravi have made no reports of anyone breaking the code of conduct and Australia subsequently used that as part of their defence. Gibson, however, believed that the umpires must have heard something.
"The match officials are there to do a job and to govern the game on the field, and off the field I guess," he said. "If they hear things on the field, they should clamp down on it. It becomes unfortunate when everybody else hears stuff and the match officials say they haven't heard anything. They are there to do a job and they must do their job.
"If things are happening in the game and things are being said, and if it's within earshot - if the player is standing at point or wherever he is fielding, surely the umpires can hear. Maybe the umpires need to stand up and take control of the game.
"Unhappy might not be the right word. We just feel that the umpires are there to do a job and they must do their job. When they hear things, they must take charge and don't leave it to: 'oh, we didn't cross the line.' Can you say whatever you want, and then when something is said, it's offensive. You didn't tell us where the line was. Let's be clear where the line was."
With tension escalating on both sides, the umpires' roles will be in sharp focus once again in Port Elizabeth. Dharmasena will be the on-field official again on Friday and he will be joined by New Zealand's Chris Gaffaney.
"I am happy with aggression being shown on the field if it's coming from the bowler," Gibson said. "If a fast bowler is bowling bouncers and trying to intimidate batsmen, to me that's aggression. When everybody else is chirping or sledging the batter as he is trying to bat, that's not aggression in my book. That's how I grew up, playing the game in the Caribbean. But, obviously, things change."
Gibson recalled the West Indies greats of the past, who "didn't have to (say anything) because they were aggressive with the ball and their body language, and that's what aggression is. When a batsman is trying to take his guard and people are standing around and saying whatever they want to say, I'm not sure that it's necessary.
"If a bowler has tried everything he can to get a batsman out and he can't get him out because a batsman is playing well, and then they have to revert to that, then is it aggression? I don't think that it is."
That was the case at Kingsmead, where de Kock scored 83 and partnered Aiden Markram for a sixth-wicket stand of 147 which stalled Australia's victory push and dragged the match into the fifth day. De Kock had not struck a half-century in 15 Test innings before that, and there were questions over his form. But Gibson believed the Durban knock showed what de Kock is capable of, both with bat and in his conduct.
"It takes a strong character to stand up and bat for three hours when everybody on the field is saying whatever they want to say to you. But then, as soon as you respond, then it's a different thing. The game should be about cricket on the field. I feel like everybody needs to focus on cricket. Calm down and get back to cricket."