Comment 2 for bug 863017

Sorry for the delayed response.

The video that you linked too does accurately demonstrate how I use xchat to connect to ustream. As far as the PRIVMSG, that was found during the development of a chat-bot side project. Early in the development of the bot, I had it dumping the raw data it received from the chat room. Most every chat packet that comes from ustream's IRC is formatted as follows:

:chatnickname!<email address hidden> PRIVMSG #channel Hello everyone I said something in a ustream channel.

This is the same information that the xchat.server command receives and what the regex filters to produce the nick and msg.

To get a clearer picture, you can use wireshark to capture a ustream chat conversation and examine the protocol structure.

I hope this helps!

(also, just for further info)
when sending a message, my chatbot sends either "PRIVMSG #ustreamchannel something to say to channel" or "PRIVMSG chatnickname something private to say to only one person"