Answer
Rashi's Talmud commentary is unique in that it has been included in every edition of the Talmud since the 1520s. This is because Rashi's commentary is considered to be one of the most important and influential works of Talmudic scholarship, and it is essential for understanding the Talmud. Rashi's commentary is also known for its clarity and accessibility, making it a valuable resource for students of all levels.