It's apparently due to the fact that Direct2D includes its own font antialiasing independent of ClearType, or something of that nature. There are cases where it

It's apparently due to the fact that Direct2D includes its own font antialiasing independent of ClearType, or something of that nature. There are cases where it dramatically changes the feel of the font, though. In particular, arial bold gets exceptionally bold in some places without any change in kerning, resulting in a jumble of color all smushed together.