I keep typing ... A-l-i-c-e- -C-o...
As soon as I type the first 'o', itunes suggests "Alice COOPER", and autocompletes what I'm typing; and it helpfully capitalizes the 'o' I just typed too. I literally could not find any way to get itunes to accept "Alice Cooper" into the box via the keyboard. I resorted to typing Alice Cooper in notepad, and using paste in iTunes as the ONLY way to fix the artist name.
A few versions back that dialog box worked just fine.
That's just one tiny example that represents an entire CLASS of grief I have with apple software these days. I run into the same sorts of grief all over the place.
Even clippy was less annoying... at least it asked if you wanted help, and you say no, and you could even turn it off. Apple now just assumes you need help, won't let you say no or turn it off, and won't even let you fix its incorrect guesses. UX idiocy.
You know, I'm seeing that in Safari on my MB Pro. I have a home-brew photo database with a web front end, and for picture #1 I might type a caption like, "skater types on slashdot", then for the second picture which happens to be of me, I'll type in "skater". Then it fills in the "...types on slashdot" and I have to fight with it to keep that part away. I thought it was because my computer is running slowly and I was typing quickly, but it sounds exactly like what you're seeing.