using "s3cmd -F sync src dest" causes symlinks at src to always be copied to destination regardless of whether or not they exist at the destination.
The expected behavior would be for it to not upload files that already exist at the destination, like it does with other files.
This looks like an easy bug to fix. Change the line
sr = os.stat_result(os.lstat(full_name))
to:
if cfg.follow_symlinks:
sr = os.stat_result(os.stat(full_name))
else:
sr = os.stat_result(os.lstat(full_name))
Fixed in 1.5.0 I believe.