The problem with elegant backwards compatibility with ASCII is that few systems ever stuck to ASCII - everybody used different, incompatible extensions to ASCII, like the ISO 8859 family and codepage 1252. So by being elegantly backwards compatible with ASCII, UTF-8 also manages to be subtly incompatible with the majority of almost-aSCII data that exists, in ways that <i>sometimes</i> don&#x27;t matter. Until they do.