Great, that's the type of info I wanted to get before going forward. I guess
there's code relying on the binary representation of 'S' to do mmap's or access
the array's raw contents. Is that right?

There is a fundamental semantic difference between a string and a byte array,
that's the core of the problem.

Here's an alternative that only handles the repr.

Whenever we repr an array using 'S', we can instead show a unicode in py3. That
keeps the binary representation, but will always show the expected result to
users, and it's only a handful of lines added to dump_data().