A classic, for sure. The page is still there: https://groups.google.com/g/shibboleth-users/c/EjvS2Cgio6c

When you're native at a language, you often don't realize that you're using an idiom. By that I mean when you use an expression that means something different to what the literal words mean.

Here's one I was thinking of the other day. In German, to breathe is just a verb: atmen. But in Danish, it's an idiom: at trække vejret. If you just found the straight dictionary definition of "at trække" you would find "to pull". "Vejret" is the weather. So if you didn't know that bringing the two together meant to breathe, you would end up being confused.

It gets worse if the idiomatic phrase has grammatical significance. "I used to eat meat". If you only just learned a bit of English, you would wonder what "to use" in past tense meant that had to do with the rest of the sentence. Or perhaps you would theorize that a word was left out (eg using a fork to eat meat). But you'd be completely wrong, since what it actually means is that I stopped eating meat, though I had done so for a period in the past.

My guess is that Japanese is far enough away from English that early translating software couldn't figure out these kinds of things. By contrast, I've never had modern LLMs write anything that didn't seem native, presumably because they are complicated enough to absorb the knowledge from the training data.