What are "threads"?
A "thread" is a group of messages in a conference that share the same subject. The messages that are part of the thread may be scattered through the message area, and the conversation "threads" its way through the other messages. They are most often created when people reply to other messages -- if you don't change the subject when you reply, your reply will be part of the same "thread" as the original message.
What is "thread mode"?
When you click on any of the three "thread" buttons, you are placed into thread mode. Now you will see only messages that are part of the same thread. The normal Prev and Next buttons will not work until you leave thread mode. To leave thread mode, click on the standard Index button.
How do I leave thread mode?
Just click on the standard Index button (not the "Thread Index" button) and you'll return to the list of messages from your current conference. If you have frame view enabled, you can also click on a link to another message from the frame displaying the index.
Why are messages on the same subject in different threads?
The subject line determines what "thread" a message is in, and to be in the same thread the subject lines much match exactly (only capitalization is ignored -- spacing and punctuation are important). Thus, the subjects "Lecture 2", "Lecture two", "Lecture 2.1" and "Lec. 2" are all part of different threads. However, "Lecture 6" and "LECTURE 6" would be in the same thread.
Why isn't the high message pointer changed?
While you are in "thread" mode, the high message pointer will not be changed. That way you won't accidentally skip messages because you thought they were old, but you'd just skipped past them while reading in thread mode.