Terminal Encoding Not Working For Certain Characters
Huh.  Sure enough, it's not setting up VT100 line drawing by default, and apparently programs don't bother with little things like how you're supposed to send enacs before using smacs any more (no doubt because some Linux terminal emulator doesn't require it, therefore "nobody does").

Anyway, quick fix (here, at least) is to add to your ~/.bashrc

test -t &amp;&amp; tput enacs