Prints a notification every time someone is caught using a debuff that's not allowed. The allowed debuffs can be configured in the Custom Options tab.
If you want the notification to go to the raid chat instead of printing only to your chat window you can enable the relevant option in the Custom Options tab.
Some exceptions are hardcoded: Mortal Strike on Lethon and Ebonroc, Shadowburn below 3%, various stuff on Chromaggus due to vulnerabilities.