The attached picture shows inconsistent anti-aliasing fonts on KiCad v5.1.9 menus (you need to see the figure without scaling to see the difference, such as saving figure on your computer and not seeing it through your browser).
If you do not see that in your Win10, this is because Win10 has anti-aliasing fonts by default, and it may mask (blur) that inconsistency.
I was able to notice this inconsistency because I am having disabled the anti-aliasing feature on my Win10 (to get sharp fonts on Win10 without unnecessary blurriness).
To disable the anti-aliasing, edit the Computer\HKEY_CURRENT_USER\Control Panel\Desktop\FontSmooting value in the registry, and set it to 0 (a restart is required for the change to be in effect).