Is the Oxford comma optional or incorrect in Swedish?
It's incorrect. (or at least the recommendation is not to use it).
sorry but, what is the Oxford comma?
A comma used before and in enumerations: A, B, and C. In English, you can use it or not, some people have very strong opinions about it. In Swedish, the recommendation is not to use it.
Please remove this one, it's so easy it's annoying and extremely boring if it gets asked 100 times.