I think everyone can understand that if people were simply allowed to emend or delete texts based on their own understanding, not a single talmudic tractate or medieval work would emerge unscathed. As such, the only honest thing for an editor to do is to point out in a note how he feels the text should read, or if he thinks that a passage should be deleted. Unfortunately, ArtScroll did not choose this to follow this honest, and common sense, approach.
It is not just Rabbenu Tam who dealt with this matter. Nahmanides, in commentary to Bava Batra 134a, blasts those “sinners” those who emend texts based on their own understanding.
וזו עבירה גמורה ולייטי עלה רבנן כל מאן דמגיה ספרים מדעתא דנפשיה
R. Abraham ben David (Rabad) also leaves no doubt as to his position, stating that one who deletes a text based on his understanding, “his hand should be cut off, since one who deletes [sections of] books is like those who burn the Torah.”
ויד המוחקת תיקצץ שמוחק הספרים כשורפי התורה
Marc B. Shapiro, “More About Rashbam on Genesis 1 and Further Comments about Artscroll”, The Seforim Blog (8 June 2015) [http://seforim.blogspot.com/2015/06/more-about-rashbam-on-genesis-chapter-1.html]