As per Adam's comment (#11) the Xft.rgba resource value definitely triggers this issue.
Adding Xft.rgba: none to your .Xresources file fixes the font width issue.
Alternatively, for quick testing, you can do: echo "Xft.rgba: none" | xrdb -merge
I've attached a screenshot showing the difference between values "rgba" and "none" for this resource.
As per Adam's comment (#11) the Xft.rgba resource value definitely triggers this issue.
Adding Xft.rgba: none to your .Xresources file fixes the font width issue.
Alternatively, for quick testing, you can do:
echo "Xft.rgba: none" | xrdb -merge
I've attached a screenshot showing the difference between values "rgba" and "none" for this resource.