Actually, it does look like it's messed up in your screenshot. Notice the quote mark on "sad" doesn't appear to be two spaces from that guideline? Do some more indenting and see what it looks like. Here's an image to check out as well:
On the left, size 10. On the right, size 9 (and I added some padding after seeing your screenshots). You can really see how the guidelines slowly shift (or rather the text does) the more you indent. I think that is happening in your XP screenshot.
I was thinking that it must be a font issue at that size in Windows (rather than an ST2 display problem), but I downloaded Notepad++ to see if I could recreate the issue, and it displays fine there... (booo)
I'll create a new thread and see if others have ideas. Thanks for your help in testing!
UPDATE: I created that new thread, so we can move any other conversation about it over here: viewtopic.php?f=3&t=6957