The other day I read a remark on the ending of Mark and the "asceticism" of B and Aleph by Streeter (The Four Gospels, 337):
"Since B Aleph were written in the fourth century, both the Longer and the Shorter Conclusions were already of great antiquity, and can hardly have been unknown to the scribes who wrote these MSS, and, for that matter, to a fairly long succession of MSS. from which they were copied. Incidentally I may be permitted to remark that an asceticism which could decline to accept either of these endings argues a fidelity to a text believed t obe more ancient and more authentic, which materially increases our general confidence in the textual tradition which these MSS. represent."
Another passage that comes to my mind is Matthew 6:9-13 - The Lord's prayer, and the absence in this textual tradition of a concluding doxology (of whatever kind) that was also of great antiquity and surely in liturgical use very early (cf. Didache 8.2, more remotely 2 Tim 4:18 - and various ancient liturgies). How great a temptation to add a doxology, or at least an AMEN - the prayer ends so abruptly with the "Deliver us from evil".
What other examples of major "textual temptations" can you think of?