One of the classic discussions among the commentators of the Talmud is between Rashi (11th century) and his nephews, known as the Tosafists. There are many famous discussion between them but in this blog we focus in Safrut and there are two classical discussions pertaining to this subject. We will deal with one of them in this post.
Rashi and Tosafos disagree in regards to the exact shape of the letter Chet in the Jewish Alphabet. A very short briefing: The Talmud says that there's a special "tag" (sketch) on top of the letter Chet, which points upwards symbolizing that God, who's up in the heavens, is eternal since the letter Chet is connected to the word "Chai", to be alive. Rashi and Tosafot explain differently the shape of this mystical sketch.
Rashi says that it is a simple sketch in the left side of the Chet like this while Tosafot says that there's a "pyramid" (a.k.a. "the hunch of a camel") in the very middle of the letter like this , essentially two connected Zains (you can see the original page of the Talmud, where this discussion is to be found, here)
That means that the grandsons (Tosafists) had a different Torah Scroll than their grandfather (Rashi), a striking fact. And the Halachic implication of these two versions is not simple - a Sefer Torah that has some Chets like Rashi and some like Tosafot might be pasul, so the rabbis decided to adopt a "blend" of the two versions, which we still use to this very day: (my own hand-writing). The Sephardim have a slightly different version -> .
But this is not the end of the story. A few hundred years later the Ariza"l (16th century), the most revered Kabbalist, introduced a few changes in the letters of the Torah and one of the affected letters is the Chet. Instead of two connected Zains, the Ari wrote the Chet with a Vav and a Zain, like this .
Clearly, the Chet is the most controversial letter of the Hebrew alphabet and now you know why!