Fade animation in Impress - doesn't work on Mac

Using Impress on Mac, the fade-in custom animation fails to space and
smooth/alias/hint the fading text correctly until it finishes the effect.
This causes the text to jump into place at the end of the animation.

I've verified this on two Macs, running Mountain Lion (the effect was
present in Snow Leopard too). LibreOffice 3.6, 4.0 and now 4.1 display this
behaviour, though 4.1 fails, the effect looks different (presumably due to
Core Text?). The same files look great on Linux - smooth text, fading
correctly. Windows doesn't smooth/alias/hint the text, but fades OK.

This situation means I can't use fades in Impress on the Mac. Any advice?

Apologies if this has been discussed elsewhere - a search didn't show
anything.