The light from the sun seems to make the moon disappear during the day. As it gets brighter out during dusk, the moon slowly fades until it disappears.

This is an intended feature.

Making the moon the disappear during the day, is an intended feature?

Yes. Because moon can rarely be seen on day.

I'm sorry, but that's not true. The moon is up during the day, 50% of the time.

http://earthsky.org/space/when-can-you-see-a-daytime-moon

And here's a million pictures to prove it:
https://www.google.ca/search?q=picture+of+the+moon+during+the+day&client=safari&rls=en&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiAptfkktDJAhVK6oMKHYmDBhYQ_AUIBygB&biw=1377&bih=902#tbm=isch&q=moon+during+the+day

;-)

If you want to hide things during the day… I would suggest hiding all the Planets except Venus (at dusk and dawn). THOSE aren't visible during the day to the naked eye. The TWO things you should be able to see during the day, are the Sun, and the Moon, and that's it.

What I mean by visible was over certain brightness compared with neighborhood.
Maybe our naked eye can see the moon, but it cannot be simulated on optical calculation.
But venus can still be visible. It cannot be seen by naked eye because it is point source unlike moon.

I was under the impression that you were coding it to make it disappear during the day. Did you code it to make it disappear during the day?

No, What I did was just setting moon not too bright.

What do you have it's apparent magnitude set to?

Default is the magnitude of the Moon.