Dear Rov. Why do people seat in the shul during the Hakofes of Simchas Torah?, is it not prohibited to remain seated when a Sefer Torah goes by next to us?

One has to stand when a Sefer Torah approaches (Shulchan Aruch Y.D. 282: 2). This applies even when one is occupied in learning Torah (Pischei Teshuva ibid. 3). However, if the Sefer Torah is being held or carried in a separate area of the shul such as the elevated Bima one is not obligated to stand (Shulchan Aruch Y.D. 242: 18). The same would apply if one is seating in a separate area of the shul. Horav Shlomo Miller’s Shlit’a opinion is that one may remain seated in need when separated from the rest of the shul by a full size common Shtender (movable pulpit that holds a Sidur etc.). The Rov added that regular Shtenders have the shape of a small door and is seen as a separation. Horav Aharon Miller Shlit’a pointed to Mishna Berura (102) that quotes opinions to be lenient when seating next to a person davening Shemone Essrei, that is usually prohibited but permitted when one is very tired or in pain.