I'm not a native English speaker, but I don't like to use that as an excuse for any quality issues with my comic. I've been living in the US for almost 20 years now. At this point, I'm more comfortable thinking and speaking in English than in my first language. XD
I understand this can be a legitimate concern for those who don't live in an English-speaking area, though, or for anyone whose situation may be different from mine.
My current comic is a bit of a unique challenge. The majority of the dialogue is canonly spoken in Korean (of which I am a native speaker). Since I'm primarily writing for an English-speaking audience, I try to write in English from the get-go instead of writing in Korean first and then translating, but sometimes the dialogue just pops up in my head in Korean... and translating is HARD even when you're fluent in both languages! I feel like I kind of dug my own grave with this one OTL
To make matters worse, one of the main characters speaks a specific dialect of Korean, giving him a very prominent accent. I had to create a fictional English accent in order to at least SORT of capture that feeling because I can't imagine him not having an accent. The fictional accent has grown on some readers, but not all, and it's become one of the least popular creative decisions I've made with this comic. But I'm sticking to my guns because in a character-driven comic, preserving character is a goal worth taking a risk for.