A first attempt at sorting 

     zort_key     |                  text
------------------+----------------------------------------
  0019Z           | Top comment
  0019 0022Z      | Top reply to top comment
  0019 0022 0012Z | Top response to top reply
  0019 0022 0001Z | Meh response to top reply
  0019 0006Z      | Earliest reply to top comment
  0003Z           | Less highly rated comment
  0003 0005Z      | Reply to less highly rated comment
  0000Z           | Crap comment that nobody wants to read