The Ibn Ezra is not only in one place. It is in five or six, IIRC. Also IIRC, the most revealing occurrences are in Yeshaya at the beginning of perek mem, corresponding to the suggestion by bible critics that from that point on, Yeshaya was written by others.
I’m not certain how controversial this even is, since the gemara says that Chizkiyahu and his disciples wrote Yeshaya. I just took a quick look at the gemara (BB 15a) and the Gemara and Rashi are using (heaven forbid) historical evidence to support the authorship of certain seforim.
(Note: I looked into this a few years ago and I think what I’ve written is accurate but it’s been a while.)