> Terms of service have no legal binding unless both parties agree to them.
Companies are perfectly entitled to tell people they aren't allowed to use their services anymore. That's what the C&D was. It's perfectly legal to say "here's an API anyone can use, except you, Anish Kapoor."
It's like if Reddit bans you, you aren't entitled to use the site after they've told you you're banned. Even if you can find a technical means around the ban, it's still trespass.
In the EU you can ask your country for help with FB/reddit/whatever bans.
IANAL, but if I were a lawyer, I would be making the case that Nitter is not using X's services. Nitter is no different than Firefox or Chrome, it's a user-agent acting on behalf of the user.
> if Reddit bans you, you aren't entitled to use the site
I would say that you are not allowed to use their site as a logged in user (i.e. upvoting, downvoting, commenting, making posts).
It does not seem logical to me that Reddit could "ban" anyone from using their public frontends as anonymous users.
They could only do something like that, in my opinion, if access to all their content was gated behind a login.