A few days ago, loaded up a ranked match, and after the game I was hit with a 2 week suspension and told to relog to see details. When I relogged I was presented with my Champion Select chat, In-game Chat and Post Game lobby chat. It was pretty easy to deduce that the jokes I made in champion select got me banned, which was very surprising. I understand why banning players for what they say in-game would make sense, you don't want to cause arguments, or distract your team members or unnecessarily cause problems, but the stuff I said was neither distracting, nor too offensive, nor was it said during the game, I generally try my best to keep myself and other players focused on the game.
This is mainly a heads-up, since I personally had no idea that saying certain things in champion select was against the rules, champion select and post game lobby always felt more private than in game chat, this new rule being implemented feels like a secret and and invasion of privacy, it would have been more helpful if Riot gave notifications in the client when this rule was introduced.
The jokes I made in champion select did contain offensive words, and I believe that was the main reason I was banned. Of course, now that I know saying certain things against the rules in champion select is against the rules, I'll keep that in mind, I just don't believe Riot Games communicated that rule properly since it was never like that in the past.