If I use
exiftool -tagsfromfile "Folder A/%f.%e" -all:all "Folder B" -m(Synchronizing EXIF Data (https://exiftool.org/forum/index.php?topic=4393.0))
I don't make copy of my EXIF UserComment in photo.
How I can change command-line?
It works correctly here
C:\>exiftool -G1 -a -s -r -UserComment Y:\!temp\x\y\z
======== Y:/!temp/x/y/z/Folder A/test-1.jpg
[ExifIFD] UserComment : test-1.jpg
======== Y:/!temp/x/y/z/Folder A/test-2.jpg
[ExifIFD] UserComment : test-2.jpg
======== Y:/!temp/x/y/z/Folder A/test-3.jpg
[ExifIFD] UserComment : test-3.jpg
======== Y:/!temp/x/y/z/Folder B/test-1.jpg
======== Y:/!temp/x/y/z/Folder B/test-2.jpg
======== Y:/!temp/x/y/z/Folder B/test-3.jpg
3 directories scanned
6 image files read
C:\>exiftool -P -overwrite_original -tagsfromfile "%d/../Folder A/%f.%e" -all:all "Y:\!temp\x\y\z\Folder B"
1 directories scanned
3 image files updated
C:\>exiftool -G1 -a -s -r -UserComment Y:\!temp\x\y\z
======== Y:/!temp/x/y/z/Folder A/test-1.jpg
[ExifIFD] UserComment : test-1.jpg
======== Y:/!temp/x/y/z/Folder A/test-2.jpg
[ExifIFD] UserComment : test-2.jpg
======== Y:/!temp/x/y/z/Folder A/test-3.jpg
[ExifIFD] UserComment : test-3.jpg
======== Y:/!temp/x/y/z/Folder B/test-1.jpg
[ExifIFD] UserComment : test-1.jpg
======== Y:/!temp/x/y/z/Folder B/test-2.jpg
[ExifIFD] UserComment : test-2.jpg
======== Y:/!temp/x/y/z/Folder B/test-3.jpg
[ExifIFD] UserComment : test-3.jpg
3 directories scanned
6 image files read
What is the exact output from exiftool when you run your command? Are you using exiftool to see if the UserComment has been copied or some other program? Are you sure the originals have a UserComment tag, as the -m (-ignoreMinorErrors) option (https://exiftool.org/exiftool_pod.html#m--ignoreMinorErrors) will treat non-existing tags as if they were a 0-length string.