How do I change the comment sort order? I am trying to work out how to change the order of a flat list of comments in Drupal 7. It seems that comments are listed in chronological order with the oldest appearing at the top and newer ones appearing further down. Is there some way of reversing this order so that the most recent comments appear at the top and older ones at the bottom?

There is a module called sort_comments but there is no official release version (only dev).  The constraints of the project I am working on does not allow the use of non-production ready modules.

Project constraints also prevent the use of any custom modules.  Only allowed to customize at theme layer (e.g. can create custom theme).
You could use Comment goodness it has a stable D7 release. 


  Provides comment sorting, comment form placement and comment form
  configuration settings.