I'm curious, can you show the result that you get with native 16x AA?
yes:
I magnified it for 4x (with no interpolation of course).
As you can see, there is difference between lines, but actually all they rendered with one call to the RenderWindow.Draw function with the same color. In action it looks much more ugly, because all these artifacts jumping from one line to another and it looks terribly, especially with black background.
PS: just tried to round vertex coordinates to integer and it definitely looks much better, but with some specific zoom factors, aliasing still exists. I see moire effect with moving view position and zoom.
here is screenshot with integer vertex coordinates (zoom and position is different with previous screenshot, because it's changed everytime)