DY – As has been discussed before (I think in the thread about the story of Rav Moshe and the Chalav Stam), if anything, the incident with the Chofetz Chaim to which you referred indicates that it is Muttar to speak Lashon Hara about yourself, although it may not be a good idea. [Otherwise, the Chofetz Chaim wouldn’t have done it.]
HaLeiVi- I don’t think it’s Lashon Hara to point out that someone is different, unless the way in which he is different is of a sort that it would be Lashon Hara to point out, or if being different in and of itself is a negative quality. It’s clear that when the speaker called Reuven an idiot for voting for BHO, he was highlighting what he considered to be Reuven’s poor choice of candidate (and what that choice says about Reuven). Presumably, the feeling is mutual; Reuven considers the other candidates poor choices, and he thinks that voting for them is telling about the voter.
Would it be Lashon Hara for Reuven to say (even in such a crowd as you described), “Shimon is such an idiot – he voted for Mitt Romney!”?
If the only Lashon Hara aspect is the crowd, I think it’s only ??? ???? ???.
As far as the trolling question, I meant: “Are you deliberately saying something to get me [a fellow poster] upset?” (which is what I always thought trolling meant), as opposed to just kidding. If you were trolling, there’s no point in responding; trolls are by definition not concerned with ????? ?????, so why would they care about Lashon Hara?
If you were just kidding, it nevertheless provides an opportunity to point out that the added phrase, “is an idiot” changes it from ??? to full fledged Lashon Hara.