There will be some bad words and inappropriate scenarios as a Helper, and you need to be able to deal with them acting as an adult so you don't make them worse. I'm not saying there aren't mature 9 year olds or immature 14+ year olds, but in the mid-teens is probably the best time to give a position to someone with the power to mute etc.
Being accepted for Helper is based partly on your level of maturity. You have to be able to handle things with a cool head, and not blow up.