I never got used to it is the thing. And I spent a heck of a lot of time on it. Yet I still look at a link like [1] and it may as well look like hieroglyphics to me. It's not that I can't parse it, it's just that it's like forcing me to do 500 push-ups in the process, to communicate something that shouldn't need more than 10 push-ups to warm up at most. Mathematical notation isn't all like this. Some stuff is actually intuitive. PL/proof theory notation just seems to be actively designed to make your life harder for some reason.

[1] https://www.google.com/books/edition/Advanced_Topics_in_Type...