Picture states the problem
#Door guest room
sweet flame
supple stream
That's not a bug. It means the guest is inside.
olive sand
Probably the devs never thought of why one should build the guest rooms downward like you did and "never" added a darkened texture for it
shut seal
I think it's more because the guest orders appear there ... but they could change that, I suppose
supple stream
I personally like that you see the door because if it's in the morning and you want to knock to kick the guest out, it makes it more obvious where the door is (I know there's an indentation above, but this is clearer.) And as mentioned above, guests order food and drink from the rooms. I understand where you're coming from, but this game doesn't strive for realism, so this seems in line with the rest of the game and it's fine.
supple stream
Yes, good idea. This is also connected to the issue of wallpapers not affecting doors, making walls with doors look weird unless you use the original stone brick wall texture.