It’s great that people raise the stories they have seen or heard for discussion here - this thread certainly captured my interest.
Calcium carbide is illegal in food production almost everywhere including throughout Asia. The case studies indicate the treatment of fruit with calcium carbide appeared to be a problem in developing countries, especially in open markets, and contact with this chemical also produces an acute response - it will burn your skin if touched, create ulcers, vomiting, pain and nausea if consumed and it gets worse with higher doses.
I couldn’t find any incidence or reports about this in Australia. Can you imagine picking up a banana in a local market and it burning your hand? Seems unlikely this would occur without notice.
Even though this isn’t a MythDefied thread, I’ve awarded some BS Buster badges for the efforts to explain the mysterious powder so far. Please keep posting your banana (or any other fruit) related stories or explanations here 
