Thank you for your reply!
Unfortunately, I’m not entirely sure if I understand what you mean. I already do set both sun and moon rotations in my actual project, but I didn’t include the sun in the sample project since it’s behaving as expected. Rotating the moon, on the other hand, can lead to either no lighting at all if its world yaw rotation is > 0, or lighting that is much too bright if the moon is below the horizon. I created the same scene in 4.15 and everything is working fine there. (Also, is it just me or do the clouds and lighting look much better overall in 4.15? Especially in the distance.) is another set of videos plus corresponding project files to better illustrate what I mean:
Project Files 4.15 (1 MB)
Project Files 4.16 (16 MB)
The behaviour in 4.16 doesn’t make a whole lot of sense to me. Shouldn’t the moon always contribute to cloud lighting if it is above the horizon and the sun is down? And, conversely, not contribute at all if it is a certain degree below the horizon? 
Edit: The appears to be how 4.16 handles the moon rotation. Whenever the moon’s world rotation yaw is negative - be it above or below the horizon - it is lighting the clouds. When the moon’s world rotation yaw is positive, it’s not lighting the clouds.