When reading Rashi, each comment on the pasukkim is split up by DiBur Hamatchil (quotes from the pasuk to let you know what Rashi is commenting on). Are these original to Rashi, or were they added? On a related note, wouldn't have been more helpful to put Rashi's question in its place?
Update: According to comments with better screen contrast than my own, there are marks indicating the Dibbur Hamaschil.
Here are pictures of Rashi Manuscripts. It appears to me, but maybe I'm just not seeing it, that the Dibbur Hamaschil is not in the manuscripts.
For example, check out p. 272
The Lubavitcher Rebbe learned many concepts in Rashi from the Dibbur Hamaschil. Therefore, it seems to come from Rashi himself.
The Lubavitcher Rebbe in a footnote says explicitly:
*ועפ"ז מובן גם מה **שרש"י מעתיק (לפני פירושו) את התות "וישלה יעקב מלאכים
"And now it's understood what [why] Rashi copied (before his explanation) the words "And Yaakov sent angels"...
In response to one of these questions Shmuel Brin has already commented that the Rebbe often attributed these headings to Rashi. It seems to me that many modern writers do this in the course of discussing the headings. I see three theories that would explain this: 1) They have concluded that Rashi did in fact write the headings, making headings significant and requiring explanation; 2) they don’t know whether Rashi wrote the headings or whether they are really significant, but wish to offer an explanation needed in that case; or taking a middle position, 3) they don’t know whether Rashi wrote the headings, but they see the headings as definitely significant, and just use the name “Rashi” as shorthand for “the true author of the headings, whoever that may be.”
Anyhow, the editors of ArtScroll's Sapterstein Edition of Rashi also sometimes suggest that Rashi wrote the headings. I note a few examples.
- Gen 23:02. On p. 243, note 2, “Most versions of the text treat [Hebrew phrase]… as a heading, leading commentators to question why it is on these specific words that Rashi raises the issue… If [Hebrew phrase] is viewed as a heading, Rashi’s choice of these words to introduce his comment about the juxtaposition can be explained as follows…”
- Gen 26:14. On p. 286, note 1, “Rashi appears to be defining only the word [Hebrew word]… Why then does he include the word [Hebrew word] in the headings?”
- Gen 33:18. On p. 381, note 7, “Thus Rashi places this comment regarding Jacob’s escape from Laban and Esau under the heading “Upon his coming from Paddan-aram” and not under the heading “And Jacob came intact.”
- Num 20:17. On p. 244, note 1, “The text, which includes… 'etc.' in the title, follows virtually all contemporary editions. Consequently, most of the super-commentaries on Rashi understand his comment as an explanation of the phrase “we shall not veer right or left,” which Rashi indicates with “etc.”
The notes also sometimes mention the correct headings without saying that Rashi wrote them, e.g. at Gen 37:02, p. 413 note 8 and Gen 49:04, p. 536 note 10.
Incidentally, I don’t know whom to ascribe these particular choices to, but on the title pages of this series the English translation is ascribed to Rabbi Yisrael Isser Zvi Herczeg in collaboration with Rabbi Yaakov Petroff and Rabbi Yoseph Kamenetsky. Contributing Editor: Rabbi Avie Gold.
I don't know of comparable examples from Rashi's other commentaries (on the other scriptural books or on the Talmud); I spend more time with this commentary than with those. But why would someone think that Rashi limited his headings to that one commentary and wrote no headings in the others?