I probably have too little knowledge about OSM and JOSM. Trying to learn more all the time. My goal is just to make a more accurate coastline of where I/we fly in Xplane 11/12. Normally, I use the data OSM data in the Ortho4xp folder and only save on my computer all changes, and never upload to OSM. It takes many many hours to change all the islands. If more people want to download good coastlines to Ortho4xp, it's good if you can save directly online at OSM so more people can share my work, otherwise it's just me. But as I said, I don't really understand what will go wrong because there will be double coastlines and problems.