[NTG-context] Unicode question

[Manfred Lotz]

Hi all,
If I run this minimal example

\starttext

�

\stopluacode

\stoptext


I get

tex error       > error on line 3 in file /data/tmp/u1.tex: ! String
contains an invalid utf-8 sequence

and some more lines.


The character above is:

  Character: �
   Character name: REPLACEMENT CHARACTER
        Charblock: Specials
         Category: Other symbol
          Unicode: U+fffd
             UTF8: 0xefbfbd

which is a valid utf8 character.

Questions:

1. Why is it considered to be invalid?

2. Are there other valid utf8 characters which are considered invalid?


Just wanting to understand.


-- 
Manfred