Mwoah, both the Linux port of OpenBSD ksh and mksh have issues with
UTF-8. mksh works a little bit better and even has a special UTF-8 mode.

The oksh issue has already been reported about a year ago. That's the
problem with using ports. If it works in the un-ported version (which it
probably does), you have almost zero chances of getting it to work in
your port.

Addendum, 2019-12-11: Nope! Same bug in native OpenBSD!

Giving mksh a couple more days. Maybe back to GNU bash ...

Oh, what makes these two shells more interesting than bash? The amount
of source code, for example. mksh is just a bunch of files, bash is a
lot bigger. But that's about it, I can't judge the *quality* of the
code, yet. And all of them carry a ton of obscure backwards
compatibility stuff.

I only need a tiny subset of all those functions. The same is true for
Vim.