U+201B and U+201F have zero width in Thin, Light, and Ultra-Light

[Safari77]

for i in Regular Thin Light Ultra-Light; do 
  pango-view -t "O‛O‟" --dpi=1000 --line-spacing=-1 --header --font="Spectral ""${i}" --align=left --margin=32px -q -o Spectral_"${i}".png
done
oxipng *png

201B;SINGLE HIGH-REVERSED-9 QUOTATION MARK;Pi;0;ON;;;;;N;SINGLE REVERSED COMMA QUOTATION MARK;;;;
201F;DOUBLE HIGH-REVERSED-9 QUOTATION MARK;Pi;0;ON;;;;;N;DOUBLE REVERSED COMMA QUOTATION MARK;;;;

[Safari77]

But this does not happen in LibreOffice...?