I don't like feature of many of the modern programming languages requiring strings to be Unicode and restricting many things like they mention there (e.g. disallowing mismatched surrogates, disallowing out of range values, etc). It is why I like programming languages such as C and PostScript, which don't do Unicode (there are many other good things they have too; that is only one of them). When they do use Unicode, it is annoying to have to work around it.