RichText textDecoration underline line position not correct

Steps to reproduce:
1. create a lot of text for RichText Component (I used the TLF Editor Advanced in Tour de Flex to create the Text)
2. underline some text
3. my font Verdana (Mac OS X) and fontSize 11

Actual Results:

• the gap between characters and the "underline" varies
• as you can see it on the screenshot, sometimes the gap between the chars and the line is 1 Pixel (1st line on screenshot) and sometimes the gap between the chars and the line is 0 Pixel (2nd line on screenshot)

Expected Results:

• same gap between chars and underline (1 Pixel)