why is the node id missing from the comment:edit action?
@Denford: You are right in saying that comments do have ids. They are just called cids and not nids :-)

What is the trigger that you are firing? My guess is that for a new comment posted, you are not seeing the 'cids' because they would be available only to the trigger 'after saving a new comment' and not the trigger 'when either saving a new comment or updating.. blah blah'.