Dear Hubby (DH) has a pet peeve which is one eating with mouth open. While it's considered rude in Western culture, unfortunately, eating and slurping loudly is common in Asian culture.
When we were living in Hong Kong, many people slurped and sloshed while eating. It's the same back in Malaysia. It’s not necessarily a bad thing because some people see it as enjoyment of food. Or mostly, people don't realise what they are doing.
I am working on my Montessori assignment now and read this section on teaching eating manners. How it works is that caregivers sits at each table and eats with the children, modeling chewing with the mouth closed, using utensils correctly and asking politely for things to be passed.
Which builds on my belief that children learn by mirroring the behavior of their parents.
So intuitive and simple. I will certainly be implementing this in the school.