I agree that links to comics should better go in the open thread, but this explanation for the downvotes seems incorrect--a search for "xkcd" and SMBC" shows many posts consisting of links to comics, most of them upvoted. This one was downvoted because the suggestion that the comic references LW was deemed wrong.
And I think the community's reaction was rather too harsh--it was a honest mistake by the poster, and while I can understand someone downvoting it when it had zero or few downvotes, I cannot understand someone piling on after it had been already heavily downvoted and taking it to its present value of -15, a karma score I associate with trolls, spam, personal abuse or political rants, not a honest mistake.
I cannot understand someone piling on after it had been already heavily downvoted
I vote down when the post is of a kind I don't want to see here, without regard of the post's current score. This seems to me as a more sensible voting pattern than the obvious alternative and I hope I am not applying it alone.
(Disclaimer: I haven't downvoted this post.)
I think we could apply the lessons, anyway, but Munroe might have our community in mind specifically. The alt-text refers to emotional biases. I'm just curious if others got the same impression.
http://xkcd.com/1112/