Prior to reading the Megillah on night of Purim, three blessings are recited: “Al Mikra Megillah”, “She’asa Nisim” and “Sheheheyanu”. On Purim day only the first two blessings are recited, although the Ashkenazic communities recite all three. The Mishna Berura (O.H. 690:1) writes that when the blessings are recited, the person reading the Megillah should recite them standing up. The Sha’ar HaTziyun says that even the congregants should be standing while the blessings are being said. Notwithstanding, Rabbi Baruch Toledano (Kitzur Shulhan Aruch 521:1) and Rabbi Shalom Messas (Shu”t Shemesh Umagen, vol. 1, § 63) write that Moroccan custom is for the congregants to sit during the blessings of the Megillah.
The Magen Avraham (O.H. 8:2) points out that whenever a blessing over aMitzvah is recited (“Asher Kideshanu Bemitzvotav Vetzivanu”), it is done so standing up. However, he has difficulty with the blessing that women recite overHala since the Mishna (Hala 2:3) explains that it is done sitting down. The Vilna Gaon reconciles this by saying that a blessing over any Mitzvah which could be performed while sitting could also be recited whilst sitting. Regarding the reading of the Megillah, the Shulhan Aruch (Orah Haim 690:1) rules that it may be read sitting and therefore, according to the Vilna Gaon’s explanation, its blessings could be said while sitting also.
The Magen Avraham (O.H. 8:2) points out that whenever a blessing over aMitzvah is recited (“Asher Kideshanu Bemitzvotav Vetzivanu”), it is done so standing up. However, he has difficulty with the blessing that women recite overHala since the Mishna (Hala 2:3) explains that it is done sitting down. The Vilna Gaon reconciles this by saying that a blessing over any Mitzvah which could be performed while sitting could also be recited whilst sitting. Regarding the reading of the Megillah, the Shulhan Aruch (Orah Haim 690:1) rules that it may be read sitting and therefore, according to the Vilna Gaon’s explanation, its blessings could be said while sitting also.
Summary: The Moroccan custom is for the person reading the Megillah to stand for the blessings, while the congregants sit.