The Thinking Behind The Tweet

Empathy - is it the ability to feel what someone else feels?

Or - is it the ability to understand what other people are feeling?

It seems to me Sympathy is the word for sharing feelings while Empathy is the word for understanding another person's feelings.

Does it make a difference? Yes - people may not share feelings yet be quite capable of understanding them. People may share feelings and do it so intensely they exacerbate the feelings - misery loves company. When misery enjoys company people don't accomplish constructive things. When company understands misery there is an opportunity for constructive, comfortable change.