Gordon, it looks like its been a while since you made this post. Not sure how valid it is now... I am particularly interested in the LigatureLevel.NONE value. It seems that it is no longer supported.
How do I turn of ligatures in the font rendering?
My flex project involves trying to match the font rendering of Apache's Batik rendering of SVG and ligatures have been turned off in that codebase. Is there any way (even roundabout) to turn ligatures off in flash?