The Duolingo offensive content filter is sometimes mysterious in the content it deems offensive. Here's a few Wiki articles I tried uploading in the past that I remember coming up as "offensive" for Duolingo:

http://it.wikipedia.org/wiki/Alessandro_Volta http://fr.wikipedia.org/wiki/Ren%C3%A9_Magritte http://fr.wikipedia.org/wiki/Baguette_(pain) http://fr.wikipedia.org/wiki/%C3%89rasme http://it.wikipedia.org/wiki/Don_Giovanni_(opera)

Meanwhile, I should mention that DuoBot kept uploading wiki articles of porn stars in Italian for a few weeks. I think that has been fixed now but I just wanted to juxtapose that with the stuff I've tried to upload that Duolingo has considered offensive. rofl.