If I think of it, i'll have a look on my client.
I never really paid attention, but I'm not sure one is supposed to 'see' stars that far, in any situation, and the fact that you can hover on those stars but not see them, as it seems, tends to show that. So perhaps the curious thing is that you can hover on those when you shouldn't be able to?
As for whole groups disappearing, I've seen that, but I would think that it's down to how the camera internally works. As far as I can tell, I don't recall seeing anything like this with an increased density, when I buff it up to 120,000 stars or so, I see a very dense and perfectly limited bubble of stars, no star out of that bubble and no chunks of it disappearing when I spin the map. Say there's actually no bug, it would show that the 'problem' lies in how it works and in the settings.
Then again, I should have a look with default settings. Haven't played in a while.