Right, so I looked at that paper and its citations, and I am still not seeing any studies showing that folic acid supplementation causes problems beyond "can mask signs of B12 deficiency," which is not very compelling. I did see one paper saying "we thought excess maternal folic acid consumption might lead to asthma in children, but nope, it doesn't." To be clear, my bias is actually against folic acid supplementation: we should be using bioavailable folate, at the very least in prenatal vitamins. But I just don't see any data showing actual harm from folic acid.