I found this link (https://discussions.apple.com/thread/3068040?start=0&tstart=0) that may provide an answer for you.
It would appear that only your camera needs the .m2ts.moff and .modd files; that you can delete these files from your computer once the .m2ts file has been downloaded.
Look online and you’ll find quite a bit of information regarding your “mystery” files.
Jack
