A report happy is defined as someone who feels the need to report everything they deem unworthy of the webite, even if what they're reporting isn't against the rules. If they think it should be against the rules, they'll report it.
User: My friend is a pain in the butt.
Report Happy: You're going to get reported now. Profanity is against the rules.
User: I don't like you.
Report Happy: Reported for harassment!