User blog comment:Forchar Oliath/Xenophilius, the Silver Tongue Assassin/@comment-5086858-20120713062848/@comment-4434378-20120713154015

Also: Thornmail reflects base damage, not damage after armor. So no, you would not take more damage from thornmail.

With some good damage items and crit, it wouldn't be difficult to do 400 True damage every swing. Better nerf irelia.