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My (UK) MacBook Air keyboard doesn't have # marked. It has ± and §, which I have never used, but it doesn't have #, which is an extremely common character in computer code. Instead, I have to use the unmarked OPT+3.
I'm using terminal to SSH into a remote server. And through this connection I am loading up the nano editor. In order to access certain nano keyboard shortcuts, I have to go into the terminal settings and allow "Use OPT". But then I can't type # characters.