Info: Monitor brightness TEST

[Imp]

First appologies for multi post upon reading think you were wanting line not to be visible so hope this helps though it throws a spanner in the works.

Size makes a big diffrence to the visibility of the line.
The picture you provided I can see the line just as displayed on the web page thumbnail but very clearly if I view the full picture.

However

If I run my game setting magnifcation so flag is approximately the same size I cant see the line. Infact I cant see the line at all on any magnifcaton for unit flags but I can cleary see the line at any magnification on the victory flags.

Ths is probably due to the human eye & extra width of the stripe letting your eye defne it.

Guessing here but this says to me if anything my game is fractionaly darker than yours or at least the picture provided.
Perhaps also my graphic card & or monitor is better than yours allowing the line to stand out easily to the eye once it gets above a certain size/ width.
On the gradient provided a diffrence of 3 or more along is clearly visible. In otherwords on a casual (normal) look 3 adjacent colours would not be noticed but the next would.
Considering its 20+ shades away from black it therefore stands out easily