Always careful not to scream "Bug!", but what I'm seeing on my screen is at least odd. I've made an Open Type font that can produce nut fractions, fractions with a horizontal bar between numerator and denominator. Strictly speaking these kind of fractions belong in the "afrc" feature, but I put them in the frac feature because that's the one Adobe apps support (with InDesign as main target). The feature consists of a mixture of subtitution and positioning lookups. For instance, if you type "1/23", the 1 will be replaced by a numerator, the slash by a horizontal bar twice the width of single digit and the 2 and 3 will be replaced by denominators. The 1 will be shifted to the right, to center it above the bar, the bar is positioned underneath the 1, and the 2 and 3 are positioned underneath the bar. Works fine in Fontlab, works fine in InDesign (CS and CS2). So far so good. When I checked the font in Illustrator (CS and CS2) the fraction feature only triggered the substitution lookups, not the positioning. Same result in Photoshop. Is this an example of differences in type rendering engines between Adobe apps (in this case Indesign vs AI/PS) shining through? Am I missing something in the Open Type specs? Anyone any thoughts on this?