I don't believe this is a hacking incident. There is a possible glitch in which users can use to space out the chat box in order to make it look like you are chatting something when you really are not. They use a special key command and type your name in these brackets (<namehere>) in order to make it look like your chat.
Please refrain from using swears here on the forum, but if this user happened to be saying rude things or things that are against the rules and you wish to file a report, you can take a screenshot that includes their username in the chat and send it to me via PM.
No need to worry though, the "hack" in which you are refering to is simply a glitch. Hope this clears things up.