fixup! Detail how to use macOS/GNOME keyrings for repo passwords (fixes

#392)

docs/faq.rst

@@ -349,7 +349,11 @@ Using ``BORG_PASSCOMMAND`` with GNOME Keyring (Ubuntu, Debian, Fedora)
   .. note:: For this to automatically unlock the keychain it must be run
     in the ``dbus`` session of an unlocked terminal; for example, running a backup
     script as a ``cron`` job might not work unless you also ``export DISPLAY=:0``
-    so ``secret-tool`` can pick up your open session.
+    so ``secret-tool`` can pick up your open session. `It gets even more complicated`__
+    when you are running the tool as a different user (e.g. running a backup as root
+    with the password stored in the user keyring).
+
+__ https://github.com/borgbackup/borg/pull/2837#discussion_r127641330
 
 Using keyfile-based encryption with a blank passphrase
   It is possible to encrypt your repository in ``keyfile`` mode instead of the default