Conversation so far:
What can you tell me about walking and discipline?
Cricket has for many years debated whether batsmen should "walk".
What did he say in regards to his stance on batsmen?
Gilchrist reignited this debate by walking during a high-profile match, the 2003 World Cup semi-final against Sri Lanka.
What happened in the 2003 world cup match?
after the umpire ruled him to be not out.
He has since proclaimed himself to be "a walker".
Did anyone oppose the decision?
Gilchrist's actions have sparked debate amongst current and former players and umpires.
Did any rules change based on his protesting?
CANNOTANSWER.
What did the former players debate?
whether batsmen should "walk", that is to agree that they have been dismissed and leave the field of play without waiting for (or contrary to) an umpire's decision.
Are there any other interesting aspects about this article?
In January 2006, he was fined 40% of his match fee in an ODI against South Africa.

Question: What did he do wrong in that match against south africa?
Self-contained rewrite: What did Adam Gilchrist do wrong in that match against south africa?