1. Using the xft font backend, I start Emacs like this:
   emacs -Q -fn "-b&h-Luxi Sans-normal-normal-normal-*-12-*-*-*-*-0-iso8859-1" test.txt

2. I type M-: (insert (propertize "I think this is poor rendering of `i'" 'face '(:weight bold :height 1.2)))

This is the result I get: