Quando um diretório exibe uma sobreposição de ícone de "bloqueio"?

Question

Eu quero um conjunto somente de leitura de documentos, então fiz isso:

cd ~
chmod --recursive a-w Documents

Por que apenas o ícone do diretório mais alto mostra uma sobreposição de ícone de "bloqueio"?

> cd ~
> ls -l
total 7688
-rw-rw-r--  1 roger roger 4127692 Dec  6 14:09 Backup.log
drwxrwxr-x  2 roger roger    4096 Dec 24 19:48 Backups
drwxr-xr-x  2 roger roger    4096 Jan  9 00:28 Desktop
dr-xr-xr-x 21 roger roger    4096 Jan  8 20:24 Documents
drwxr-xr-x  2 roger roger    4096 Jan  8 02:38 Downloads
drwxrwxr-x  5 roger roger    4096 Dec  7 14:07 Jts
drwxrwxr-x  5 roger roger    4096 Dec  6 13:55 programs
drwxr-xr-x  2 roger roger    4096 Jan  2  2016 Public
drwxrwxr-x  2 roger roger    4096 Dec  7 03:17 restore
drwxr-xr-x  2 roger roger    4096 Jan 11  2016 Templates
drwxrwxr-x  3 roger roger    4096 Jan  2  2016 VirtualBox VMs
drwxrwxr-x  3 roger roger    4096 Nov 26 17:42 WindowsBackup
-rw-rw-r--  1 roger roger 3691022 Nov 26 17:52 WindowsBackup.log
drwxrwxr-x  2 roger roger    4096 Nov 26 18:46 WindowsBackups
> cd Documents
> ls -l
total 92
dr-xr-xr-x  4 roger roger  4096 Dec  2 17:33 bashscripts
dr-xr-xr-x  2 roger roger  4096 Oct 28 15:14 discard
dr-xr-xr-x 35 roger roger  4096 Dec  7 00:53 doc
dr-xr-xr-x  5 roger roger  4096 Oct  8  2013 ib
dr-xr-xr-x  7 roger roger  4096 Feb  7  2016 jppf3
dr-xr-xr-x  5 roger roger  4096 Mar  9  2016 jppf5
dr-xr-xr-x  5 roger roger  4096 Oct 10 22:27 jppf5e
dr-xr-xr-x  3 roger roger  4096 Sep  4 20:35 ohana1Deployment
dr-xr-xr-x  3 roger roger  4096 Jun 28  2012 pyUtil
dr-xr-xr-x  3 roger roger  4096 Apr 18  2016 rangeTest
dr-xr-xr-x  6 roger roger  4096 May  4  2016 run140domains
dr-xr-xr-x  3 roger roger  4096 Apr 15  2016 run5domains
dr-xr-xr-x  6 roger roger  4096 Dec  3  2014 sandbox
dr-xr-xr-x  3 roger roger 20480 Jun 25  2016 sandboxDomains
dr-xr-xr-x  8 roger roger  4096 Feb  5  2016 smallPrograms
dr-xr-xr-x  4 roger roger  4096 Oct 28 15:13 systemDrivers
dr-xr-xr-x  2 roger roger  4096 Nov 28 21:17 validator
dr-xr-xr-x  4 roger roger  4096 Mar 10  2015 website
dr-xr-xr-x 14 roger roger  4096 Jan  8 20:51 workspace

Quero observar que aplicar chmod em um nível inferior não afeta o ícone relevante. Por exemplo, o seguinte não tem efeito sobre o ícone de doc .

> cd ~/Documents
> chmod --recursive a-w doc