I recently had quite a funny case with this answer that I had written. I wrote an answer that was technically wrong. Overnight, the question hit the HNQ, and subsequently got lots of attention and upvotes.
When I had returned, there were several comments, indicating that I was indeed wrong. I double-checked, since the question had received more attention, and corrected the answer.
Schroeder raised a valid point after the revision was done, in that the answer is now a completely different one, and it could be seen as a bait-and-switch. He suggested to delete my old answer, which I could not do, as it had been accepted already.
So what is the procedure for "major revisions" to answers, especially those who got accepted already?