<div>This Shabbos is Shabbos Rosh Chodesh, where during Mussaf we "combine" some of the Shabbos and Rosh Chodesh liturgy. In the Kovetz Mevakshei Torah of 5755, there was a great discussion about why it is not customary to add "Kadesheinu B'Mitzvosecha, V'sain Chelkeinu.... V'Taheir Libeinu L'Ovd'cha BeEmes", being that this is said every Shabbos, Yom Tov, and Shabbos SheChal B'Yom Tov. Apparently, R' Seraya Deblitzki did institute that it be said in his Minyan, and there was something of a consensus that our Tefillos should be emended, though others disagreed.
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<div>Does anyone know of:</div>
<div>a) A good reason this piece should not be said on Shabbos Rosh Chodesh</div>
<div>b) Any other large Minyanim or Yeshivos where it is said?</div>