I read a recent answer there whose first sentence was the opposite of reality. Thinking of how I could demonstrate this easily and effectively, where any person could follow up easily and see what's right, I posted a comment saying it contradicted the second sentence of the Wikipedia article on the topic.
My comment was automatically banned by the auto-moderator because it had a link to Wikipedia and no other links. I tried reading the subreddit rules before posting, but it's pretty hard to find this rule -- indeed, it is not explicitly stated as far as I can tell.