Wrong UTF-8 encoders still around?

[Martin J. Dürst]

I'm hoping to get some advice from people with experience with various 
Unicode/transcoding libraries.

RFC 3987 (the current IRI spec) has the following text:
   Note: Some older software transcoding to UTF-8 may produce illegal
      output for some input, in particular for characters outside the
      BMP (Basic Multilingual Plane).  As an example, for the IRI with
      non-BMP characters (in XML Notation):
      "http://example.com/𐌀𐌁&#x10302";;
      which contains the first three letters of the Old Italic alphabet,
      the correct conversion to a URI is
      "http://example.com/%F0%90%8C%80%F0%90%8C%81%F0%90%8C%82";

We are thinking about removing this because we hope that software has 
improved in the meantime, but we would like to be sure about this.

If anybody knows about software out there that still presents this 
problems, please tell us.

Thanks,    Martin.