Someone pointed out in the comments on that link that utf8mb4 isn't necessarily case sensitive. The author believed that due to the fact that he was using utf8m

Someone pointed out in the comments on that link that utf8mb4 isn't necessarily case sensitive. The author believed that due to the fact that he was using utf8mb4_bin_ci as collation, which is a binary collation. It works as expected when using a "true" collation like utf8mb4_general_ci. The index problem is mildly annoying, but limiting index length isn't a big problem. For most applications, you can uniquely identify a row with much less than 191 characters, and it might be a good optimization to limit index length regardless to prevent the index size from growing out of control. If it's truly a problem, hacks like adding a sha1 or md5 hash column with a value derived from the original column and indexing that instead solves the problem. Edit: Ops. Didn't realize parent was the article author. :)