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?
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:
"And now it's understood what [why] Rashi copied (before his explanation) the words "And Yaakov sent angels"...
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.