university level, or can I use it anywhere? will duolingo say I'm wrong if I use it?
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
The 1st option is the common one. The others are commonly looked at as "bad Hebrew" even if confirmed by the academy.
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.
I am a bit confused. All of them are male forms, right? But weren't we told that we are supposed to use the feminine forms when we are just counting without referring to real objects...?