When exporting to Vobsub position is ignored: subtitles starting with {\an8} are not position at the top of the screen. This does work when exporting to Blu-ray SUP.

Addionally, when selecting "Simple rendering" italics are ignored (both in Vobsub and SUP export). I don't know if this is the normal behaviour.

(Subtitle Edit 3.3.9, Windows 8 x64)

Should be fixed in commit r2201 - also available here: http://www.nikse.dk/SubtitleEdit.zip

The "simple rendering" is simple (old way), so it does not support bold, italic or colors - but it has some other spacing usage and it draws something in Arabic correct. Well, it seems to do well for images with only three(+background) colors like vobsub.