I have the same question as the OP and I have read the two links you posted (plus more). I haven't been able to find a definitive answer - nothing about what you do if just married or if you transmuted separate property to community property part way through the year (which is my case).
Since everything I have read does not mention prorating or splitting community property based on the date of marriage or transmutation, I have to conclude that newlyweds who file separately must treat community property as if it was owned by both spouses for the whole year.
I'll keep searching for the answer...
