World Congress - day one
Prof Mordechai Sabato discussed Mishnah Megillah 4:1. The first half of the mishnah. He showed that the tractate splits very neatly down the middle, with chapters 1-2 dealing with reading the Megillah, and chapters 3-4 dealing with reading the Torah. But the aforementioned mishnah goes back to reading the megillah. Basically, his suggestion is that it was moved there from the beginning of chapter 2 (where it appears in the Tosefta) in order to contrast with reading the Torah. That requires his slightly re-interpreting the mishnah, that it is saying the megillah can be read either standing or sitting, by one person or by more.
Menahem Katz demonstrated that, in its development of sugyot from the Yerushalmi, the Bavli will often summarize the sugya. It sounds counter-intuitive to people who are used to thinking that the Bavli is always more developed, but it makes sense.
Uri Zur read through several long sugyot in Eruvin, claiming that there were stages in the sugya that did not really make sense, but were there to allow the editors to move the sugya in a different direction.
Richard Hidary compared the sugyot about 'Lo titgodedu', the prohibition against secession, in the Bavli and Yerushalmi. Basically - the Bavli only makes sense if you read it as a point-by-point polemic against the Yerushalmi. More in his doctorate.