Can't trash some folders on live sessions

I noticed that some folders can't be removed on Xfce live sessions (slackware64-live-xfce-current.iso):

https://www.mediafire.com/convkey/bf...od5m72hhzg.jpg

If I confirm to permanently remove it, then comes a new dialog saying the folder is not empty and it fails to remove it.

Maybe there's a reference (symlink?) to these 'untrashable' folders somewhere...?