We get this in a fresh moose image, on OSX:

This is really a pity.

This problem is so important, that we may directly output a roassal visualization in a separate window, bypassing Athens and directly using Cairo on SDL.

do you think that it will solve your problem? I do not think so. I will just make the system more complex. You should not have a direct dependency to SDL else you will break the idea behind OS window.
What will happen if the platform does not have SDL installed like my machine?
The solution is to try to get a reproducible case else how can we try to fix when it does not happen on our machines
and also to try to see if using a different fonts is actually resolving the problems.

Stef