Lack of transparency when it comes to moderation is a bad thing. If a user is getting punished for breaking rules, they should be shown exact the message that led to the action, so that users can't claim they got banned for no reason or for some vague reason about community standards.
Also, I've never been a fan of immediately going nuclear and banning people for their first rule violation unless it's especially egregious. A simple "Hey, we don't do that here" and a short period of time-out can be a lot more effective for changing behavior.