I found this answer that I provided that was just wrong, but is the accepted answer. Should I have deleted the incorrect answer and provided a new one, or was editing the answer the proper course of action?
Typically I'd say you should delete your old answer and add a new correct answer. But because of the type of question, and the fact that most people are likely voting you up because you're quoting from the NEC, I think it's appropriate to just edit your question. I suspect these votes are an acknowledgement of your expertise in the area more than an agreement that they have also read the appropriate NEC codes and know you're referencing the correct one.