"Seuls vous, pouvez manger."
Duo is very casual about punctuation when assessing student responses. If they continue overlooking dropped commas, periods, question marks etc., as they do, then they have to be sure you understand the intent of the phrase by how specific your translation is.
Only you, can eat suggests that of the people who want to eat, only one person will be able to eat. You alone, can eat suggests the same thing_.
However, You, alone, can eat indicates that the person can eat if they wish but they will be alone when they do regardless of whether anyone else is present and who may or may not wish to eat.
Without placing a high burden on students to display excellent punctuation standards the only recourse is to require more exact translation to convey the meaning.
With or without proper punctuation only conveys the apparent, intended meaning of the phrase.
I'm confused... So is the comma needed for proper English translation? I did not place a comma but my answer was accepted, so was there an update (meaning, with or without a comma, the translation is acceptable) or was I incorrectly marked as right?
"Only you, can eat" is a sentence structure I have never seen nor used before in any medium (it looks wrong; I remember something about rules in inserting commas to separate clauses... "can eat" cannot be alone in a clause.).
"Only you can eat" makes more sense with the grammar lessons I have been taught since I was a child (it means "you, alone, are allowed to eat, but the others are not.").
The punctuation problems all seem to come from months ago, if the comments are something to go by. So maybe there was an update? :o