I think the instruction here could not be mistaken.
I went to the toilet on my KK-bound flight today and opened the door to find somebody was in the middle of doing her business. I am not sure if I was more suprised than she was.
I mean, what the hell? I had to keep my head low to avoid any eye-contact with her. I didn't want her to be embarrased.
But I could not avoid it when I had to queue up for the immigration check.
And true enough, she flushing all over when I happened to see her, and she to me.
Kidding. She was lucky. I couldn't recognize her. But seriously, you should always check if you have locked the door properly EVERY TIME.