"He eats lunch?" and "Does he eat lunch?" have different meanings (to me anyway). I would ask "He eats lunch?" much like I would say "He's writing a book? I don't believe it!" I think it is fairly common to rhetorically ask things that way informally, especially with a verbal emphasis on the subject, "he" in this case, and a rising inflection -- it communicates a kind of surprise or disbelief, often when you are restating something just said to you, but as a question.
I assumed maybe there was a different way to do this in Danish, so that's why "He eats lunch?" was rejected, but as far as I know, it's a grammatically fine answer in English.
Oh, I hear ya. I notice, though, that your second hypothetical example is in a different form than the first. "He's writing a book?" is different and performs a different function in that context than "He writes a book?"
I understand what you mean now, though. I'll leave it to native Danish speakers to answer the question of how they would translate your idea.
Indeed! I do agree though, and I think a better example would be something like saying, "He drives a motorcycle!?" after you see your boring boss drive away on his new sports bike after work :D
I'm not sure that kind of snarkiness would translate cleanly across languages but I am mighty curious now!
I'm still a bit lost on grammar. Why is it not "Han spiser frokost?" I thought it was usually: Subject Verb Object. My guess is that in this order it implies it's a question?
I've so far ran into another example that didn't work like this, but that was explained because there was an adverb so it was really Adverb Verb Subject Object, "Måske snakker han engelsk."