I have Kannada text in my column and it's not working, but it worked fine with Latin text before. Kannada text is from a region near India. Here is my spreadsheet, there are too many rows to include in this post.
word frequency ಮತ್ತು 71520 ಈ 40233 ಒಂದು 25255 ಎಂದು 17046 ಇದು 15032 ಅಥವಾ 14527 ಹಾಗೂ 13709 ಅವರು 12979 ಎಂಬ 10660 ಮೇಲೆ 10581 ಅವರ 10204 ಆದರೆ 9271 ತನ್ನ 9090 ತಮ್ಮ 8768 ನಂತರ 8672 ಮೂಲಕ 7645
The validation rule is:
=COUNTIF($A$2:$A,"="&A1) < 2
That is, on the second row onward, validate that no two cells have the same value. I double checked that the cell that has the red flag on it doesn't have a duplicate, and it doesn't, so something must be off with the way unicode values are calculated in that expression or something, any ideas?
I learned how to do this in the first place from Forcing uniqueness in a Google Spreadsheets column