Q. 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?
A. 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.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit’a.