This forum and most of the added functionality were written with the Prosilver style in mind. So if you use one of the other styles (I use Breeze), you may notice some things that don't work or look perfect. You might try switching to the Prosilver style and see if that resolves the issue. I can't fix stuff like this without doing a lot of coding and debugging or begging for someone else to do it, so it probably won't get done.
Phpbb is intentionally a stripped down forum application. You can add functionality through extensions, most of which are free. But there are limits to what you can do and what you can find for free.