Nedarim 79-80
Indeed, Shadal doesn't like im lo as shelo either. Though we can add Rashbam to shelo side, and Rashi on Shas.
Still, given that enough commentators, including peshat commentators, could take it as such, I'd credit it as a strong explanation of the Mishnah.
BTW, in the Yerushalmi parallel, we do have more named Amoraim giving the conditional interpretation. https://www.sefaria.org/Jerusalem_Talmud_Nedarim.11.1.8?vhe=The_Jerusalem_Talmud,_edition_by_Heinrich_W._Guggenheimer._Berlin,_De_Gruyter,_1999-2015&lang=bi&with=all&lang2=en
Indeed, Shadal doesn't like im lo as shelo either. Though we can add Rashbam to shelo side, and Rashi on Shas.
Still, given that enough commentators, including peshat commentators, could take it as such, I'd credit it as a strong explanation of the Mishnah.
BTW, in the Yerushalmi parallel, we do have more named Amoraim giving the conditional interpretation. https://www.sefaria.org/Jerusalem_Talmud_Nedarim.11.1.8?vhe=The_Jerusalem_Talmud,_edition_by_Heinrich_W._Guggenheimer._Berlin,_De_Gruyter,_1999-2015&lang=bi&with=all&lang2=en