Hi Pablo,

> \showframe
> \setupinteraction[state=start]
> \starttext
> \startbuffer[abc]
> def foo(x):
> if x == 0:
> bar()
> else:
> baz(x)
> foo(x - 1)
> \stopbuffer
> \comment[location=leftmargin,
> space=yes,
> buffer=abc,
> title={Python code}]
> {}\typebuffer[abc]
> \stoptext
> 
> This might solve what you need. At least, this is the approach that I
> use to provide text that can be directly copied.
> 
> I'm on Linux and last time I tested on Windows there were extra lines in
> the comments.

That's actually something I had never thought of, using PDF comments,
thanks!. 
It's a really nice approach, though weirdly it doesn't work on Okular
(Linux+KDE) 
for me, even though attachments worked fine. I'll try and see why that
is. 

What I had in mind was rather the following: 

\starttext 
\starttyping[space=on] 
def foo(x):
    y = bar(x) 
    if y: 
        return x 
    return y 
foo(1) 
\stoptyping 
\stoptext

but with ordinary char32 spaces rather than \textcontrolspace
characters. 

Best regards,