I don't know exactly since I didn't lock it... but I imagine it had to do with back-and-forth insults across the thread. I figured they were mostly in good humor in the context of that thread and no one seemed to be getting actually offended... but I can't honestly say that it was a bad decision to lock it.

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"Man lives in the sunlit world of that which he believes to be reality. But unseen by most is an underworld, a place that is just as real... but not as brightly lit... A DARK SIDE!"
-opening from Tales From the Darkside