Acts and behaviors that are considered bad manners in some countries are considered good manners in others.
For example: In China, Taiwan, belching is considered a compliment to the chef and a sign that you have eaten well and enjoyed your meal. In many others (countries) the opposite is the case.
Common sense says you should study your environment and make good judgment for yourself with regards to courtesy /bad manners around the world.
Consider it absolute bad manners to not study your environment or watch people to know what is “acceptable” and “unacceptable”. Good luck!