Have you ever read the Discord ToS and the partnered server community guidelines? I did read the latter the first time I used the word "retarded" in a self-deprecating manner on a partnered server and was called out for it. The rules are
written in a way that pretty much lets users say anything within the boundaries of the law, but the individual server owners and moderators can be held responsible for not moderating that content.
In essence, Discord's staff enforces a hidden layer of moderation behind the scenes. They contact server owners in private and point out individual members' faults and list exact words that are to be removed. In this way, server admins are encouraged to overmoderate due to the obvious imbalance (risk of losing an entire server vs losing a few users), yet they have to take flak from individual users.
I've seen server moderators removing completely legit messages afterwards and they've openly admitted that they can't risk someone perusing the chat history for ToS breaches, screenshotting individual lines of text and sending them to Discord abuse team, because Discord does not care about context, only actual words (see their anti-reclamation policy - even black hip-hop artists have been deplatformed for using the well known mother of all bad words in a positive context).