Ha, I realize this was asked this last year:
Any news?
For anyone else who wants this, @ncw suggested on GitHub using this to find dupes based on md5:
rclone md5sum remote:path | sort | uniq -c | sort -n
Hm, actually this only works for duplicate names AND md5. Need to look at JUST the checksum. (Need to look at only the first 32 chars of each line.)