If someone has already reported this I apologize. I did try to search for it but couldn't find anything with the keywords I was using.
If I enter a misspelled keyword accidentally it continues to show up in "Autocomplete" even though I delete it from the Keyword List.
I've never had this happen before. I recently upgraded to the 9.0 release.
My specific example of this behavior is when I go through to keyword basketball photos one of my keywords is Dribble. In the past I could type in dri and hit enter and it would autocomplete Dribble. I accidentally entered dri9 (the 9 is above the right side of the I key) and when I hit RightArrow to move to the next photo it entered dri9 into the keyword list. On the next dribbling photo when I typed dri it showed dri9 as the top option in autocomplete. I went into the keyword list and deleted the dri9 keyword. That removed it from the photo and from the keyword list but it still shows up in autocomplete.
I tried to see if I could remove it by entering dri9 in a different photo. This added it back to the keyword list. I went into the list and deleted the dri9 keyword again. That removed it from the photo and autocomplete again but then when I tried to enter dribble I noticed that I now had two instances of dri9 in the autocomplete popup. I continued to try exiting lightroom and backing up/optimizing the catalog and entering and deleting the keyword. Nothing worked although I now have four instances of dri9 in the autocomplete popup. There is also another keyword that it has happened on although I can't remember what it is now.
One other thing I did try using the Filter Keywords box in the keywords list and can't find dri9 anywhere.