i wrote an app using the irc chat system too.
When a new privmsg to a channel is written, i extract the nick-name from the host-mask:
user!ident@host.com
As the username is always lowercase in this case, how do i get the case sensivity name?
You need to subscribe to twitch.tv/tags capability, which gets you a list of tags attached to every message that contains the display name (if it’s set by the user) among other things. Read the Twitch IRC documentation for more information.