What are Hebrew manuscripts important to us for, today?

Question

What's the importance of Jewish manuscripts for us, today? Apparently many of these are dispersed in libraries, monasteries, and of course the Vatican, and one wonders whether there's value in obtaining them anew.

What value would there be in reacquiring them for the Jewish people (e.g. and giving to, say, the Hebrew U library or the Israel Museum)? Is there anything to be learned from these texts? Are there any unique challenges in obtaining them? Do the Christians in possession of some of these texts still feel threatened by their contents, the way they used to be afraid? (I.e. Confiscation was a means of censorship.)

Answer 1

In his introduction to his edition of Mishneh Torah which was based on Yemenite manuscripts, R. Yosef Qafih speaks at length about the value of manuscripts. Here is one excerpted paragraph, where he explains that very often manuscripts have textual variants that can simply resolve various problems:

עם הבדיקה והגהת הנוסח נוכחתי פעם נוספת עד כמה מוצדקת הפעולה ועד כמה הכרחי הדבר להחזיר עטרה לישנה להוציא דבר מתוקן ולא ללכת בדרך הכבושה אשר לסטים קודמים כבשוה כלשון חז"ל (ערובין נג ב) המדפיסים עם חזרות על אותם השבושים אשר נתקעו בדפוסים הראשונים רבות עתים דנו המפרשים פלפלו ארוכות בדברי רבנו ועם קביעת הנוסה הנכון אזדו להו כל אותם הפלפולים התירוצים והישובים והיו כלא היו ולא אימנע מלהזכיר כאן אמרת אמת אשר שמעתי מאחד מזקני תימן הוא היה אומר את דברי הרמב"ם אין צורך לתרץ אלא להבין פעמים רבות שינוי קל לא של משפט לא של מלה אלא של אות אחת בלבד ובה מתישבים הרבה קושיות ונעלמים הרבה פלפולים לדוגמא בהלכות עבודה זרה פ"ד הל' יג קדשי בדק הבית יפדו ואחר כך שורפים אותם שנ' שללה ולא שלל שמים על הלכה זו סערו סער כל משליכי בים התלמוד חכה הללו מקשים והללו מתרצים החל מהראב"ד ועד ימינו אנו אמאי שורפיו אותם הרי שלל שמים הם ועוד מאי קראה שללה ולא שלל שמים הרי לדבריו אפלו שלל שמים ואלו אספתי כל מה שנאמר סביב דין זה יש בו כדי ספרובאמת הכאח הנכון בכתבי יד תימן שורפין אותה ומוסב על עיר הנדחת ולא על קדשי בדק הבית שני חורים קטנים במם הסופית אחד למטה ואחד מן הצד ופתרו כל הבעיא הקולות יחדלון וגם כל העם על מקומו יבא שלום

As I studied and emended the text, I was again convinced of the rightness of the activity, and how imperative it is to return the crown to its ancient glory, to publish something that has been corrected, and not, as our sages said (Eruvin 53b), to "walk on a path which has been trodden by thieves" who reprint the same mistakes that they copy from earlier editions. Often commentators engaged in lengthy pilpul regarding Maimonides’ words, but with the correct text these arguments and explanations are obviated and nullified. I cannot refrain from repeating a true statement that I heard from one of the elders of Yemen. He used to say, "the words of Maimonides need no explanation, simply comprehension." Many times a simple change (not of a sentence or a word, but just a single letter) will settle many questions and eliminate much pilpul. For example, Avoda Zara, Chapter Four, Halacha 13: "The offerings for the repair of the Temple may be redeemed, and afterwards they are burned [sorfim otam], as the Torah [tr. Deut. 13:17] says ‘booty’ and not ‘the booty of heaven’." A storm raged about this halacha among all those who cast a hook into the sea of the Talmud, some challenging and some explaining, starting with the Rabad and continuing to our day. "How could they be burned if they were ‘booty of heaven’? Why did he call it ‘booty’ rather than ‘booty of heaven’ if according to him, it applies even to ‘booty of heaven’?" If I assembled everything written on this question it would fill a book. In fact, the correct text in the Yemenite manuscripts is sorfim otah, "it is burned," and "it" refers to the subverted city and not to the offerings for the repair of the Temple. Two small holes in the final mem, one at the bottom and one at the side, and the whole problem is solved, the arguments can stop and the entire people may rest peacefully. (Bohnen translation)

Here are five quick examples of answers I posted on Mi Yodeya that made use of manuscript evidence:

Difference between the RamBam and Talmud Kiddushin 82a in list of jobs that posul a King/High Priest?

When enumerating the Ketuvim, why does Ramba"m omit Ezra / Nechemia?

Why is one obligated to give up one’s life for all mitzvos only with a decree against Judaism and not just persecution?

Hundred like seventy and seventy like five

How does Rambam explain why we don't ask for rain until the end of sukkos

As you can see in the first two, the entire question fell away once the correct texts were obtained from the manuscripts. In the third, the manuscripts removed most of the question. In the last two, the variant in the manuscript didn't remove the question on its own but it set the answer in motion.

These are just five examples from my own answers here. There are many other examples on this site, some of which can be found using this search.

So manuscripts are very valuable for obtaining more correct readings of the texts under discussion, and these readings can often resolve various difficulties.

Answer 2

Manuscripts are generally useful because they are an early witness to some text and are (sometimes) relatively free of corruption or mistakes. A good example of this would be the Aleppo codex, which is now housed in Jerusalem. This text represents the best extant text of Tanakh. Other early masoretic texts describe early textual traditions of Tanakh.

Many Talmud versions today show various differences caused for various reasons: copyist mistakes, censorship, etc. Examination of old manuscripts show us what books of Talmud looked like before some of these changes occurred.

While Christian sources may have historically obtained manuscripts as a means of censorship, it is certainly not the case today. Many manuscripts from the Vatican and elsewhere have been published and can be accessed by scholars. Since we have this access (physically, or through facsimile or digitized versions), I imagine any research could be performed using them.