Interestingly, I suppose I have become accustomed to that kind of halo effect in high contrast situations (either due to something about my eyes or glasses), so

Interestingly, I suppose I have become accustomed to that kind of halo effect in high contrast situations (either due to something about my eyes or glasses), so I had no clue that the image was manipulated. It just looked like "normal" to me, since I suppose I just assume that there will be a halo around that sort of object. I was only able to observe the halo effect added from the image manipulation when I physically blocked my view of the "O" with a piece of paper, stopping at the edge of the character. When only viewing the black area the modification became obvious: there's a gradient around the "O" which fades to black. So the good news: it may not be anything about your monitor. The bad news: it may be your eyes! :)