I believe I've encountered a bug with text rendering whose circumstances aren't exactly clear to me, but I think it has something to do with the theme scope's background colour. For certain words, there is some clipping of the leftmost pixel column or so of the character. It isn't so noticeable with anti-aliasing on, but with a very small bitmap font it can completely eliminate a good part of the letter.
Here's how I can reproduce it on two computers: first set your font to be small and non-antialiased for best effect. Then set the color scheme to Twilight. Open a blank file and set the syntax mode to 'Literate Haskell' and type
ABC ABC ABC
If it worked, the left part of the A's should be cut off.
The bug only occurs, as far as I can tell, on color schemes where embedded code has a different background color than the rest of the document (it doesn't happen on Monokai for instance), and it doesn't happen in the Twilight theme if you select regular Haskell instead of Literate Haskell.
Here is a screenshot from Mac OS X: http://i.imgur.com/ItTzt.png
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