Another pain point on text AA: Many renderers mix up colorspaces on antialiasing. For example freetype assumes a linear colorspace when calculating the antialiased bitmap but AFAIK both GTK and QT apply it directly on sRGB without any adjusting. The result is apparently thickened fonts when displayed black on white and thinned fonts when displayed white on black.
Edit: Some background can be read on [0].
[0] https://www.freetype.org/freetype2/docs/text-rendering-gener...