it's harmful because it when it is wrong, then it can cause a lot of damage to the relationship. what we think others are feeling is always based on our own feelings. the reason it works, because most of the time, their feelings don't actually matter.

when bumping into a stranger, assume best intentions, apologize or say something else appropriate and move on. who cares what they actually think or feel.

the closer the person is, the more communication is warranted.