I cannot reproduce the case of "Rename, Move & Copy Files..." overwriting destination files when the source and destination match. If I use this tool to copy an album from my laptop to my NAS (where the album already exists on the NAS), nothing happens. I don't hear the drives spin up, and the modification dates on the NAS files remain unchanged. It appears that (in my case) "Rename, Move & Copy Files..." silently exits when the source and destination filenames are the same, and does not overwrite any files in the destination directory. I would prefer some sort of notification instead of the silent exit so that I know I asked for MC to do something inappropriate, but nothing is unexpectedly overwritten for me.
I just repeated this test copying files from one location on the local drive to another local location, and I'm certain nothing is being overwritten.
What I DO observe is that as soon as the Copy tool encounters a singe file where the source and destination match, it stops instead of merely skipping over the offending files. For example, if I copy an album to a new location, delete the first and last track then copy the album again, the first track reappears, but not the last track. This leads to annoying behavior if you're not sure which files at the destination are duplicates (i.e. my NAS seems to have 10 fewer music files than my laptop...I wonder which 10 of my 10,000 files I missed?). When using "Rename, Move & Copy Files..." to Copy, I would like MC to skip a file if source and destination match, but keep running through the full list of requested files to see if indeed there are any other source that still need to be copied from the full initial set.
OSX 10.9.5, MC 21.0.8