Aside from telling the user: "Don't move from A: to A:" ...
Interesting logic challenge. Perhaps you could send a zero-byte file (similar to mounted.bin) with a random name 4723sdf080hhev897w4thihs.bin to remote: then do a find or rclone ls on the local to see if a) the file exists and optionally b) the time stamp is identical. Then delete the random bin file.
Rclone will detect this if you try rclone move remote: remote: but it is really difficult to check in the general case - you'd have to look in /proc/mounts for an rclone mount - that will tell you if the mount point "/gmedia/hosts" is under "gcrypt:" or not
Sorry as I have $LOCAL configured up above so if they change the environment variable, it works through the script.
So a bit higher, I have:
# Local Drive
# This must be a local mount point on your server that is used for the source of files
# WARNING: If you make this your rclone Google Drive mount, it will create a move loop
# and delete your files!
# Make sure to this to the local path you are moving from!
LOCAL=/local