(I saw this write up in a discord and looked into the matter. Seems to be some pretty serious legal stuff and there is only a benefit for opting out).
In short: Discord recently updated their Terms of Service (https://discordapp.com/terms) and revoked your right to sue them for any reason. Hopefully you'll never need to, but should they fuck up in some extreme way I'm sure most people would want the option.
The good news is you can opt out of this clause and it won't affect your account or how you use the service. All you need to do is email firstname.lastname@example.org within 30 days of the ToS update (which was 2 days ago) using the email associated with your account and something along the lines of "I'd like to opt out" as the content. No additional information is necessary.
For more information see the Reddit thread: https://www.reddit.com/r/discordapp/comments/9p5uyp/latest_tos_update_revokes_your_right_to_sue/