News readers are not to be confused with readers of news, i.e., the user. A poster may issue a followup to an earlier article or start a new thread on a different topic. Replies are visible only to the recipient, just like any email. Just like followups , the sender may quote the recipient's earlier lines and comment on them. Most news readers allow an easy method for sending replies.
News readers uses the final definition.
Virtually all news servers carry these hierarchies, wherever in the world they may be. New copies will be posted eventually.