The Talmud, in discussing whether the practice of refraining from engaging in business with worshipers of Avoda Zara (lest they offer thanks to their Avoda Zara) three days prior to (and according to R IshmaelYishmael also: following) their holidays (cf. Mishna AZ 1:1) includes the day of the holiday itself in the count of three days, states (AZ 6a and 7b):
אמר רב תחליפא בר אבדימי אמר שמואל: יום א' לדברי רבי ישמעאל לעולם אסור
R Tachlifa bar Avdimi said in the name of Shemuel: the first day [of the week] is always forbidden according to the opinion of R IshmaelYishmael.
However, the uncensored version states:
אמר רב תחליפא בר אבדימי אמר שמואל: נוצרי לדברי רבי ישמעאל לעולם אסור
R Tachlifa bar Avdimi said in the name of Shemuel: Christians [lit. נ[ו]צרי Nazarenes] are always forbidden according to the opinion of R IshmaelYishmael.
[Not only is the uncensored version upheld by manuscripts (see below), it also flows better in the Talmud, which goes on to ask:
ואי ס"ד הן ואידיהן, האיכא ארבעה וחמשה דשרי!
If you think [the day itself is included in the count of three days] then the fourth and fifth [days of the week] should be permitted!
The Talmud is clearly understanding Shemuel's statement as forbidding all the days of the week, a read borne out by the uncensored text (which still ends up counting days from Sunday). (One could reread this into the censored text, by understanding לעולם to refer to the whole week, with the claim being that the whole week is forbidden because of the aforementioned holiday on the first of the week (such indeed is Soncino's rendering). This sounds unnecessarily forced IMHO.)]
The Meiri (Ta'anit 27b) is clear that he had the uncensored text in front of him, though he understands נוצרי to refer to the people mentioned in Jeremiah 4:16. This explanation is troubling because I haven't found anyone else (after checking Rashi, Radak and both Metzudot) who understands נצרים in that verse as a nationality as opposed to a job description, and secondly it seems odd for Shemuel (~750 years after Jeremiah) to reference such an obscure people who may not even have been around anymore. (See Christians, Noṣerim, and Nebuchadnezzar's Daughter Lawrence Zalcman, The Jewish Quarterly Review, New Series, Vol. 81, No. 3/4 (Jan. - Apr., 1991), pp. 411-426 who identifies the Meiri's group as the Mandaeans.)
Screenshots of manuscripts:
It's interesting to note while this censorship is not noted in Mesoret haShas in the classic 1880 Vilna edition of the Talmud (link), it is mentioned in the new 'redone' Mesoret haShas in the 2008 Neharda' edition of the Talmud (link, note 3).
Additionally the new Mesoret haShas brings a variant of Rashi to the censored sv. יום א' which accords with the uncensored text of the Talmud, and takes a clear stance against the Meiri's understanding of the word:
נוצרי: ההולך בטעותו של אותו האיש שצוה להם לעשות להם יום איד בא׳ בשבת.
A Christian: who follows in the mistake of that man [a common euphemism for Jesus] who commanded them to make themselves a holiday on the first day of the week.
I don't currently have access to any manuscripts of Rashi to verify (though itThis variant is confirmed inattested to by Dikdukei Soferim). and in a manuscript:
