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This almost certainly isn't true, it's far more likely you've only noticed it when it worked. Every other time, when it didn't, the comments were buried at the bottom of the article.

Or is it just that most comments don't get downvoted, especially well-written ones?

I'm pleasantly surprised (a lot depends on which people happen to click on the link), but was totally willing to spend 20 or so karma to say that.