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.
Please inform yourself. In these comments and on their website, it is covered that they do not provide books freely. Just like any other library books can be borrowed exactly as many times as they own a copy.
Just like any other library they sometimes provide a download for Adobe Digital Edition, which manages your lends on books. But as your friend with DRM stripping tools for sure can confirm: DRM is just an annoyance for legitimate customers, it forces legitimate users to use specific applications, while pirates get the freedom to choose how they interact with the not any more protected media. But this is a discussion for another thread as archive.org treats copyrighted books just like any other library.