1. Why do we no longer differentiate between letters with and without a Dagesh during Kriat Torah and Tefila? Why do we no longer use this correct pronunciation? 2. I understand differences among Sefer Torah’s have been found among Jews from different communities. Why has there been no movement to correct these errors? Doesn’t the slightest error render the scroll Pasul? 3. I understand the Temani Tanach is the most accurate, why do we not use their text as the core manuscript to print from?
1. Some people no longer differentiate between letters with and without a Dagesh simply because they haven't learned "dikduk"= Hebrew grammar. The correct pronunciation should be used, both for Kriat Hatorah and for Tefila. However, if the Dagesh was not emphasized, it doesn’t change the meaning of the word and therefore it need not be repeated during Kriat Hatorah. Nonetheless, the Ba'al Koreh must prepare properly. (See Shulchan Aruch Orach Chaim 142:1 ) 2. Due to our dispersion in Exile, some sifrei torah were written with minor variant spellings. Over the generations, there have different been attitudes towards these differences. It would be an injustice to try to give a full scope of the issue in this framework.( I suggest seeing the Tshuva of Rav Ovadya Yoseph Shlita, Yechaveh Da'a't Vol. 6, 56, who also discusses the accuracy of the Yemenite Sefer Torah. ) 3. The text of the Tanach which is followed today is mostly based upon the work of Ben Asher who was one the Ba'alei Mesora who lived in Tiberias in the mid tenth century, which is accepted as the most accurate manuscript. (See Rambam Hilchot Tefillin , Mezuza, Sefer Torah 8:4) This is assumed to be the famous Keter Aram Tzova manuscript which was in Allepo, Syria for generations. It eventually made its way to Yerushalayim and is now printed by Hebrew University and called "Keter Yerushalayim."