To a stranger, it looked like Jonny was cheating on his girlfriend. In reality, he was so appalled that he was dating a woman who used the wrong "you're" that he made up an excuse to get rid of her. Cheating was just the first thing he could think of.
And the Good Samaritan of the Year Award goes to... Steph! For outing a bunch of assholes and making train rides from Philadelphia more bearable in the future. Steph, you are doing the work of an angel.
Maybe don't publicly out a woman who's holding a bow and arrow. It sucks that she's cheating, but pissing her off might not be the best move. Unless you literally can't live without her. Then go for it!
"Aww, that's so cute! You look exactly like the guy in this stock photo. Do you have a twin brother running around? Yeah, you definitely have a twin brother who's married and does cute things with his wife."