

However, if you rename or postprocess a photo on your phone (modify it), then the change WILL propagate to your laptop.

This way if a new 3-rd party file gets added to the laptop or anything gets modified or deleted, the phone won't get it. Just to let other people know, for the particular usecase above, you can (sort of) get what you want with existing syncthing features if you set your phone DCIM folder to Send Only (or Folder Master), and you set your laptop to Actions > Advanced > ignoreDelete = true. You want modifications or additions or deletions on the laptop to NOT be synced with your phone's DCIM folder. You want deletions on the phone to NOT be synced. You want new photos from your phone to be backed up to the laptop. Usecase example: You want to sync your phone photo library. Instead it should pull the files from the remote folder(s) only if the files don't already exist (in a modified state or original state) OR the files didn't already get specifically deleted by the user in the Receive Only folder. Data security and data safety are built into its design. 5 It can sync files between devices on a local network, or between remote devices over the Internet. What most non-advanced users would expect is that a Receive Only folder does not delete or revert anything or make any changes to the contents already there. Syncthing is a free, open-source peer-to-peer file synchronization application available for Windows, macOS, Linux, Android, Solaris, Darwin, and BSD.

I believe the behaviour of "write-only folder type" #3780 is not what common users would expect from a Receive Only folder.
