Just because you are guitar nut doesn't mean you play guitar; it justs means that you know a freakishly huge assortment of stats and trivia about guitars. Assuming Carl means it when he says he is a guitar nut, I would have to say that pointing out the details is not bad form, but merely what is expected of a guitar nut. In fact, I think it would be bad form for a guitar nut to see such a blatant yet completely trivial mistake and then let it pass. To Carl: keep on reading, researching, and, you know, whatever it is you do.