Clearly he's an idiot [...] much safer now. - Downvote.
Oh, erm, you were being sarcastic. Dangerous. If there's no hint of the real message and if the nonsense appears to be in earnest and oblivious to irony, how many will take the extra second to read the rest?
This is where the Reg voting system is a problem. Why can't I withdraw a downvote without giving an upvote? I don't want to give either here!