Since I’ve updated to Yosemite folding text renders text a bit unpredictable when it comes to the font weight. As you can see in the attached screenshot. Thing is that if you scroll down to the paragraph that has a thinner font weight, it appears in the right font weight. And this way paragraphs change appearance on and off. Very distracting.
The thing to note is that I’m on a retina macbook!
PS: I’m on the latest app store version of Folding Text