The problem in the linked article barely scratches the surface of the issue. You _cannot_ compare Unicode strings for equality (or sort them) without locale information. A simple example: to a Swedish or Finnish speaker, o and ö completely different letters, as distinct as a is from b, and ö sorts at the very end at the alphabet. A user that searches for ö will definitely not expect words with o to appear. However, to an American, a user that searches for "cooperation" when your text data happens to include writings by people who write like in The New Yorker, would probably to expect to find "coöperation".

This rabbit hole goes very, very deep. In Dutch, the digraph IJ is a single letter. In Swedish, V and W are considered the same letter for most purposes (watch out, people who are using the MySQL default utf8_swedish_ci collation). The Turkish dotless i (ı) in its lowercase form uppercases to a normal I, which then does _not_ lowercase back to a dotless i if you're just lowercasing naively without locale info. In Danish, the digraph aa is an alternate way of writing å (which sorts near the end of the alphabet). Hungarian has a whole bunch of bizarre di- and trigraphs IIRC. Try looking up the standard Unicode algorithm for doing case insensitive equality comparison by the way; it's one heck of a thing.

People somehow think that issues like these are only an issue with Han unification or something, but it's all over European languages as well. Comparing strings for equality is a deeply political issue.