Yes but No. For most people writing this kind of mail should not be a problem. However, for many different reasons it can become difficult to write such things: This mail is some kind of formal letter and alters a contract. Let’s imagine someone with a learning disability, they may be able to sign up for a online service, as they have done it many times. Writing a formal letter they may not have done many times and they cannot map past experiences the same way as a neurotypical person.

Depending on the local law this may be a reason why forced arbitration has to be opt-in: Typically the law should protect the weaker party. As the barrier for writing this letter is higher than the sign-up process, there is an argument that the chosen opt-out process of discord is targeted against some of their weakest customers.