pwBPD can be amazingly empathetic! It just tends to be short-lived. They struggle to handle their own emotions so much they can hardly handle anyone else's. Still, they can surprise us. I once exploded into tears over a computer virus at a time my bf was suicidally depressed. I was so overwhelmed with my own problem I didn't have it in me to validate his. And I didn't care if he got mad. I was expecting him to add drama to my dilemma, but instead he was warm, sweet, positive, encouraging, offering to help.
They do allow us our 'moments' from time to time. Perhaps it makes them feel less alone to see others suffering? Or maybe it gets them away from their own problems temporarily? Mine has been amazingly comforting at times, but it doesn't last long. He expects me to bounce back quickly to get back to
his issues. By the next day, it was all woe is him again. So enjoy the empathy while it lasts!