I know such a guy...he is a nice guy...but he didn't realize it's bad to brush teeth/spit into the kitchen sink( a shared one), it's considered not hygienic because here people usually put used cups, forks, and dishes there. And brushing teeth should alwasy be carried on in the bathroom/restroom. some other guys are often found chewing/eating loudly (bia1 ji1 zui3, it's really embarrasing...and they don't realize it...but I don't know how to tell him...we are not close...I wish he can see my posting here and don't need to know who I am...sometimes it's some habit...we have to admit...It might be acceptable in China, but won't here..since we come to Rome, we might want to behave like a Roman.