[texdoc] Weird behavior of `texdoc'

[Karl Berry]

    but the underlying texlua interpreter.
    One for dev-luatex at ntg.nl, perhaps? Karl, Manuel?

I'm not sure yet.

I reduced the input to a one-line file, call it /tmp/test.txt:
a → b

And then running 
  env LANG=en_US.UTF-8 texlua /tmp/test.lua
with your test.lua, which calls less, gives the bad <xx> result.

But if I change test.lua to the one line
  os.execute('cat "/tmp/test.txt"') -- instead of less
the output is correct for me (given a UTF-8 terminal font, of course).

Also, if it was a generic problem, every UTF-8 character would be
rendered incorrectly for everyone. But we've never received a single
report before this. It seems ... unlikely.

I don't suppose it could be about that particular UTF-8 char?  --karl