You Want to Know How NOT to Get Banned for Chat?

Whatever offensive thing you want to say to another player, just say it out loud. Don't type it into the chat box. Just say what it is that's on your mind. I've done this quit a bit myself. Because the game can be frustrating and made more so by ally mistakes.

Insulting players in chat isn't going to make things better for anyone. But saying what you're thinking aloud will, at least, allow you to vent your frustration and anger without risking punishment.

Unless you happen to be in a voice chat with your team in which case I'd suggest muting your microphone for those instance in which you need to say something like

"Oh my fucking god, this jungle is fucking trash!"