So that syncs to my server, and my desktop/laptop. I drag files around on there when I want them deleted off my phone and archived somewhere. Me and my wife share a syncthing folder between us when we want to send files to each other.

All of this produces a fair number of duplicate files, particularly if you have backups turned on in case of deletes.

Offline dedupe basically makes all of that free though - duplicate files on the server or in backup dirs are no longer a problem.