What constitutes an "exact duplicate"?

Question

Recently, one of my answers was deleted from this question:

Why "meth-", "eth-", "prop-", when there is "uni-","di-","tri-"?

My best guess as to why is that it was considered a "duplicate" by the moderator. I'll agree that my answer was similar to that of another person, who referred to the prefixes of names of "organic substances."

My answer was more specific, insofar as it referred to counting carbon atoms, a term that the other person didn't use. That's a non-trivial additional point, at least to someone who has studied chemistry. I experienced a "light bulb" moment in my head when I looked up my own answer, after having read the other (and not benefited from it). Even if the content was similar, I believe that the greater clarity of my answer made it "distinct."

Can an answer that makes an important additional point be considered a duplicate? Or was my answer deleted for some other reason?

Answer 1

The question is asking why the Greek numerical prefixes are used in naming these compounds instead of the Latin prefixes; i.e. the nature of the etymology of these names.

However, your answer addresses how one uses these prefixes, but it doesn't address how they originated. That's why your answer was deleted.

Generally, we don't delete answers that are duplicates of other answers unless the new answer has essentially been copy-pasted from the original.

Answer 2

Your answer doesn't explain the origin of those prefixes; therefore, it's not an answer to the question being asked. It is also wrong, because meth- doesn't mean "with a carbon atom."