This is a really interesting thread.
Being British, I'm a native English speaker of British English, and I have a degree in Japanese. I've found that if the dialogue is going to be primarily in a language, it's a lot easier to think it in that language than to think it in your own and then to translate, even with say, British English to American English, because I feel like it'll come across in the drawings. Your whole posture can kind of change when you speak another language, or there are phrases that would make a really impactful beat panel in one that you just can't quite translate. Like in Japanese, just saying a person's name without an honorific for the first time can be a really powerful beat panel on its own... and in English it's like... okay, he said her name, what's the big deal? The rhythm is just so different.
It's like... if I'm drawing a panel, and I know the person is saying: "Ah! Sakura-chan, genki?" it feels weird to draw it while thinking "this person is saying "Hi, Sakura, what's up?"" because... it feels like the bodylanguage or posture for saying those phrases is so different? Anyone who speaks two languages can probably vibe with this, how it's like switching modes.
I think even if you're switching between British and American English it's a thing. If I'm drawing an American character saying "Hey, dude, what's up?" I wouldn't draw it while thinking, "Areet, mate what's t' craic?" (That's my native Cumbrian dialect Northern English. Yes, it's completely unintelligible to even a lot of native English speakers) they're almost different languages; American English often has a different rhythm, and uses different words, but also the whole way the voice is placed in the mouth gives it a different "posture" when you speak it.
I think it could be used to great effect if you're making a comic for an English-speaking audience, but want it to feel authentically like it's in another country or community, to think of the lines in the native language first and then translate, making it feel like the English reader is reading a translation.