Pencil Markings that Remain in a Torah Scroll
Question
In a Torah scroll, during the Torah reading of Shabbat, it was discovered that they forgot to erase the mark that the corrector made with a pencil to one side of the line of text. Is it permitted to read from such a scroll? What is the law regarding marking a letter? And what is the law regarding a mark (which is not a letter)?
Answer
Peace be upon you,
Even though Maimonides wrote that if one extra letter is written in a Torah scroll, the scroll is invalid, the Noda B'Yehuda wrote that this is only if it is written within the line in the order of writing. But if it is written from the side, it does not invalidate the Torah scroll.
Source
Maimonides (Laws of Torah Scrolls Chapter 10 Law 1. Responsa Noda B'Yehuda, Mahadurah Kammah - Yoreh Deah, Section 74