"Mishum" as Inserted Commentary
The other day, in Bava Batra 135:
אֲמַר לֵיהּ אַבָּיֵי: אִם הֵקַלְנוּ בִּשְׁבוּיָה – מִשּׁוּם דִּמְנַוְּולָא נַפְשָׁהּ לְגַבֵּי שַׁבַּאי; נָקֵל בְּאֵשֶׁת אִישׁ?! אָמַר לֵיהּ רָבָא לְרַב נָתָן בַּר אַמֵּי: חוּשׁ לַהּ.
Abaye said to him: If we were lenient with regard to a captive woman, due to, among other reasons, the fact that she makes herself repulsive before the captor so that he will not want to rape her, and we assume that she was not raped, should we be lenient with regard to a married woman? Rava said to Rav Natan bar Ami: Be concerned about it. Do not permit this woman to remarry until the matter is clarified.
The explanation of מִשּׁוּם דִּמְנַוְּולָא נַפְשָׁהּ לְגַבֵּי שַׁבַּאי may not be part of the original Talmudic text. As Rashbam writes ad loc.,
דמנוולא נפשה לגבי שבאי - לא גרסינן ופירוש היה בספרים:
We don’t have this as the correct Talmudic girsa, and it is rather an explanation, that is as a commentary, in various manuscripts.
Why does this matter? Well, if you read the Artscroll footnotes, they provide three different explanations for how a captive woman case would be different. Maybe all three are true and should be applied in other cases where they are relevant. Alternatively, perhaps only one of them is true.
Looking at manuscripts, we see a mixed bag of including (sometimes with slightly variant text) or not including. Thus, the Vilna Shas printing puts it in parentheses, presumably based on Rashbam, while Venice has Pesaro printings have it, though Pesaro has מצוו are a typo for מנוולה:
Munich omits it. Paris and Escorial include it:
Firkovich skips it, Vatican 115b includes it, and the fragment listed below includes it.
Finally, there is Hamburg 165:
which includes it, but then has a strikethrough over the phrase, which is accomplished via the shmitchiks (") placed over each word.
Anyway, this is a nice demonstration of the process of an explanatory commentary, which might initially appear on the margin, being copied into the main body of Talmudic text.