https://en.wikipedia.org/wiki/MDY_Industries,_LLC_v._Blizzar....
Yes, TOS are not legal documents. We all know that. That doesn't make Discord beholden to granting everybody the same access to their service. I don't know why people feel the need to bring the law into it; it was never relevant to start with, so making a point of it is unhelpful.
It's against the terms to use the user api (although it will work until you get caught), I'm not sure if they explicitly ban 3rd party clients (they very well may) but this effectively does the same thing.
Bot on normal account detection is based on outlier usage statistics from regular accounts, like too many requests or something.
All Ripcord requests (to discord) actually have Ripcord in their User Agent header, discord can immediately detect it's usage, they have not banned anyone for using the software specifically, only for the same reason they have been banning Selfbots (Users ending up spamming the API)