That is great news, dionoea!
dionoea's results have been duplicated! amic successfully connected to his Kindle 4 (no Touch) over usbnet with ssh, following dionoea's instructions posted above. amic does not have a /test directory, so it appears that dionoea has a "special" kindle. UPDATE: amic reports that he DOES have a /test folder after mounting the first partition.
when in diagnostic mode, yifanlu
warns "don't choose random options". This is considered a "Developer Mode" (for experts), and a true jailbreak is still being sought.