Then you have the german ß (sharp S) which does not have an upper case version. While ISO added one for whatever reason the official upper case is two letters consisting of either "SS" or "SZ". So you have three different ways to upper case ß one which is guaranteed to be wrong in any official context and two which lower case to "ss" or "sz" and not back to ß. That is one big ouch, especially to the ISO standard adding that invalid upper case variation. Languages are messy, best don't try to transform your input text in any way.
>It's used in typesetting sometimes, and if a character is used then it should have an encoding.
IMO there's little semantic difference so it doesn't deserve a character. We should have drawn the line between content and formatting, but it's too late and what we have now is emoji and one-use glyphs. [1]
