Comment 7 for bug 227808

If you're still seeing this problem with ":set backupcopy=yes", then I'd definitely push the bug to gvfs/fuse. Even if that still exhibits the behavior, I'd be inclined to think this is a bug in gvfs/fuse. Yes, Vim's behavior is not the same as other editors but that doesn't make it wrong. A properly functioning filesystem should be able to give Vim enough information that it can replicate the permissions of the original file.