This feels like a giant waste of energy that could be put into better causes. The number of people who are eligible to opt out now (those who already opted out in previous iterations) is microscopic compared to Discord's wider user base, and I would be absolutely shocked if a single person involved in this actually ends up suing Discord either individually or as part of a class.
Whether or not you believe forced arbitration is bad, it seems like there have to be higher value causes to get up in arms about right now.