On 2013–08–02 Philipp Gesang wrote:

>     https://phi-gamma.net/pdf/copypasta.pdf
>     https://phi-gamma.net/files/copypasta.txt
>   
> I definitely get   from this
> one.

Indeed. When I copy from your file I get those private Unicode
slots. When I run the example code from your OP, I get the correct
characters. I don't know what's the difference between those two
files. The LuaTeX version and ConTeXt version is the same.

Creator:        ConTeXt - 2013.08.01 01:31
Producer:       LuaTeX-0.76.0

Marco