...regardless of font size.

Its an mx:Text object. (The Text object is actually being used as a mask so don't know if that's the problem.) If underline is set with the <u> tag in Text.htmlText, or Text.textField.setTextFormat, the underline thickness is always just one pixel which is not acceptable. (There are other problems with <u> so I'm limited to using setTextFormat currently.)

Can the thickness of an underline be set through CSS? (textField.styleSheet, etc.)

I may have another problem as I already use setTextFormat extensively, and the documentation says you can't use textField.setTextFormat if you use textField.setStyleSheet.

I primarily need the underline to simulate correctly the look for an anchor tag.