Vote to mute
Disclaimer: This is not a great idea, it's a brilliant idea
Who hasn't ever wanted this option before? Sure we could all mute the player by ourselves but what better way to let the toxic player know he's being toxic than a live vote being cast like a surrender vote for muting a player. Possibly if you are voted to be muted by X% of your games you will be suspended from chat for a period of time.
Sure you can think of a million things wrong with this but who cares you are now voted to be muted