From what I've seen, Duolingo doesn't grade punctuation (at least, not in the Hebrew course, which is the only course I've done so far).
Edit: I just found an article by the Academy of the Hebrew Language talking about it. It says it is not used, and offers three alternative ways of writing a sentence:
1) No comma before the letter Vav. Example: אני קונה תפוזים, תפוחים ותותים
2) Repeating Vav several times in a list instead of commas. Example: אני קונה תפוזים ותפוחים ותותים
3) The last member in a list may come with a comma before it instead of Vav. Example: אני קונה תפוזים, תפוחים ,תותים
Based on what sample of languages?
It seems to me a strange assertion, since AFAIK punctuation was introduced into European languages long after they existed as languages. They adopted it from one another, and Hebrew adopted it from them; I think it uses pretty much the same punctuation marks of most European languages. Indeed it seems to me (from the little I get to see) that Arabic uses less punctuation, but I'd say it's a cultural thing, or maybe an institutional decision of the powers-that-be of Arabic, and not related to it being Semitic.