I thought acetylene welding and cutting nozzles were made of copper!
Yes, made by people who know exactly what they are doing and why, and have decades of experience behind them to show it's safe.
Also these things get a little bit warm and copper acetylide never gets a chance to form in any amount, it being heat sensitive, which is a bit different to a length of copper pipe bodged into an acetylene hose and lying on the floor.