In https://bugs.launchpad.net/bugs/665459 it was reported that hunspell has layout problems with very long lines (also pointed out in the manpage). \"xorho\" has created a patch for that.
Thanks for considering!
This patch no longer applies to 1.3.2, but the problem still seems to be there.
updated patch to apply FWIW
Fixes the issue I was seeing.
Ticket moved from /p/hunspell/bugs/167/