Eating is an intimate experience for everyone. The act of nourishing your body with what it needs to survive and keep you in a healthy state is something that shouldn't be taken lightly.
However, there are some people who are out to ruin it for everybody. By making too much noise, or not realizing how bad something may smell for the rest of us, they impose their bad habits on the rest of us.
Whether these are the lifelong grievances that you have let build up over the years, or if you are only noticing them now (sorry) these are the absolute worst things people do with their food.