GNU Emacs 26.0.50.1 (x86_64-unknown-linux-gnu)
Repository revision: 6bf83218314db1c63ce34564edfb994d9431b28a
Debian GNU/Linux 8.6 Jessie
xfonts-terminus 4.40-2 as shipped in Debian

Steps to reproduce:

   $ emacs --quick --font '-*-terminus-medium-r-*-*-20-*-*-*-*-*-*-*'

Find some document with curly quotes: ‘’ and “”.  GNU Emacs Manual (‘<f1> r’) uses them heavily, for instance.

It looks wrong: