>Adding more characters to the coding string may actually shorten the result even more - like adding lowercase, accented etc.

One problem with using the upper 128 characters in the extended ASCII set (i.e. character codes 128-255) is some of those characters are used as "lead-in", "shift-in" and "shift-out" character in various Asian languages (that is if the field in question is regular character field rather than binary character). I'd run into situations where a string literal containing characters in the upper 128 codes (entered using ALT+nnn keyboard sequence) would work OK in English (and likely other language using Latin character set), but when you switch the non-Unicode configuration to something like Chinese, Japanese, or Korean you end up with either a syntax error or an error indicating a non-terminated string constant (which one of these errors is dependent on the context where the string literal appears). The most confusing bit is you get these errors in a compiled program. On the other hand, if you replace the string literal with expression like CHR(nnn), the error does go away.