This is also `emacs -Q`, with `(set-face-attribute 'default nil 
:height 110 :foundry "unknown" :family "DejaVu Sans Mono")` and 
`variable-pitch-mode` disabled.

The fact that Emacs displays the word correctly with DejaVu Sans 
Mono seems to suggest that it's not an Emacs problem but rather a 
font problem, but note that the same diacritic with the same font 
displays correctly in a pdf: