Most LibraryH3lp chat spam comes by way of AOL or other spam bots on an IM gateway. If it gets to be too much, you can just not use those features, or you can block the offender's screen name in the native IM application (AIM for an AIM bot, for example).
Troublesome human behavior in the widget, such as messages from children sending prank chats, can be blocked during the chat. You can also block after-the-fact using the Activity/Chat History page in the admin dashboard. We can also block these for you on our end, just email us at firstname.lastname@example.org.