There are surely many, Kwiki-Purple does a lot of rooting around
in places where it maybe ought not.

* Some units in the formatter are not written out correctly when
  Kwiki::Purple attempts to write content back to disk after 
  adding nids. titledhyperlink is one such example, there are 
  others.

  This is a big bug as it means some content you created is now
  just plain gone.

  One way around this problem may be to only do nid adding and 
  to_text operations on blocks, rather than everything. Seems
  sort of special case'ish, though. It would be nice to address
  all units with the same interface.