If you:

• click to edit a post,

• make some changes to the post and save the edits as a draft (using the 'save' button which shows up even in 'edit' mode) and

• load and submit the draft, the edited post gets posted as a new reply rather than replacing the original post.

I think the save feature should either be unavailable in edit mode, or should save an edited post in a way so that when the edited post is finally submitted as a live post it replaces the original post.

For what it's worth, we had a discussion about this point here: http://area51.phpbb.com/phpBB/viewtopic.php?f=4&t=27492