There are a lot of things that can go wrong when working with Unicode data. Some examples of unmeant behavior:
You try to downcase "I" to "i", but your Turkish friends want it to be a dotless "ı"
Your UI is broken, because people use empty usernames, despite the String#blank? check
You think "C" is the same letter as "С", but your system does not think so and crashes
Using ten characters as representatives, I will highlight some Unicode characteristics which require a programmer's attention and demonstrate how Ruby's solid Unicode support can be of useful assistance!