In context: Discord is widely considered a relatively private communication channel compared to the open web. However, in a bid to revive the usefulness of forums, the company will start making some messages more public in the coming weeks. Server admins should now start seeing new controls to determine which chatrooms and messages can eventually appear in Google search results.
Answers posted after mid-December to questions in discoverable Discord servers can appear in search results on the open web. Usernames and avatars won't appear next to the messages, and admins can already opt out of the new policy.
Most Discord servers will remain relatively private, inaccessible to search engines and anyone without an invite. However, users can already enter certain large servers, called Discoverable servers, without an invite, and Discord aims to make information from and about these servers more visible.

Discoverable servers must have more than 1,000 members, be more than eight weeks old, and meet certain safety and privacy requirements. Discord's website already hosts links to some Discoverable servers, along with brief descriptions of them.
All discoverable servers will have web-accessible description pages starting November 16 unless admins opt out. Admins can limit public access to certain channels, but Discord will automatically generate default descriptions for discoverable servers if admins haven't written their own or adjusted the relevant settings by the deadline. The new controls can be found in Server Settings > Web Presence.
Furthermore, answers to questions posted in public channels will appear in server web pages and search results starting mid-December – if admins and users don't opt out. Channels where messages can go public will be labeled. The new system applies only to questions and answers posted after mid-December, and usernames and avatars will be hidden.

Users can opt out now by heading to User Settings > Data and Privacy. If users change their visibility settings after posting public messages, those messages will still appear on the web and in search results unless deleted. However, new messages will remain private.
The change aims to make troubleshooting solutions and other helpful advice more widely available. Although public forums still exist, many users complain that troubleshooting threads and other informative discussions have migrated to private Discord servers, making them harder to access and putting them at risk if the servers close.