The only reference to the talk button is:
All you have to do is type a message into the Chatterbox text box and click "Talk".

To me that implies talk is only used for sending messages. Now that I know it will not submit an empty message I can refresh the box without being annoying.

I propose making adding "To refresh the chatterbox simply click on the Talk button when the text entry box is empty." Or somesuch.

The talk button is fine for people who read the chatterbox faq, but most users don't read documentation.

I'd suggest the most usable solution would be to reword the talk button to read update or something similar. To me, this suggests that the box can be used to update the conversation as well as to participate.

Let us compromise, then.
The Chatterbox title could be a link to the chatterbox faq.

If the Chatterbox title is a link to documentation about the chatterbox, users will expect the other sections' titles to be links to their documentation.

I find the Perl Monks site very usable: the main reason for that is its consistency. I disagree with knobunc that the title should be clickable.

Note: I'm not suggesting that users should ignore documentation. There is already a clear pointer to the chatterbox faq, but users ignore it. Modifying an interface that users frequently misunderstand is better than documenting the cause of that misunderstanding.