"Prediction is very hard, especially about the future" --Yogi Berra
Starfirebird, thanks for your question and your very good remark on lightning. There is much more to say about lightning, but you have made a great start.
With regard to Elenin, I suppose we have to wait and see just how much charge it carries, if any. Because it is a small comet without an exceptionally large coma or tail, it is difficult for me to imagine more than the most minimal effects. In my initial reasoning, I assumed that surplus negative charge from the comet would diffuse into the electrosphere, creating the conditions when the usual fine summer/fall weather would balance the effect with more coronal discharge from earth to atmosphere. I'm reluctant to get into the stickier issue of more thundercloud formation over land, partly because it'll be the wrong time of year for thunderstorms and lightning in North America. Because lightning occurs much less frequently over water than land, it is conceivable that storms like hurricanes which deliver a lot of rain without much lightning could develop in order to maintain Earth's electrical balance. Hurricane season will still be in effect at the time of Elenin's passage. But I am not predicting a hurricane!
Respectfully yours,
Dotini