Once he figured out what it was and that it was based on distance, he had a little fun with it. He would sit next to attractive women. It was voyeurism to the extreme. Sometimes it was innocent. Sometimes they were really dealing with something intense. Sometimes they immediately became unattractive for the sake of their vapidness.
Occasionally he could use his newfound power to his advantage. If only he was a salesman, it would have been gold. As it was, he won a couple arguments at the bar.
Mostly it just confirmed for him what he already knew: that people were complex, and stupid, and egocentric, and desperate for love, and troubled, and innocent, and anxious about things they shouldn't be worried about, and thoughtless about the things they should be focused on.
Then the thoughts turned into others' thoughts and their accompanying feelings. That's when it started to become a real burden. He often had to move around. Train rides were sometimes intolerable. There was once a meal at his favorite restaurant involving a nearby couple trying to save their marriage with a tortured date night. He had to leave his food and some cash on the table and leave.
Then the effective distance started to grow.