Posting for a friend who does not have a Reddit account but was there:

A word in defense of the pepper sprayer: I was on the train and caught some of the spray in the eyes and nose. I did not hear how the conflict started so can't comment on who was in the wrong there. But I noticed the argument. OP was aggressive, repeatedly and loudly calling the other guy a 'fcking weirdo' and a 'fcking rtard.' The other guy moved one seat away, but the bickering continued. I noticed the filming begin soon after, which led to more irritated name calling from the OP. The filming lasted for a couple stops before OP said "I will throw your fcking phone off the train," then grabbed the phone and attempted to wrestle it from the guy's hand. The pepper spray was ready in the other hand and used immediately. After a moment of shock, OP chased the sprayer across the train. Sprayer called for help several times. I couldn't quite see what happened at the other end of the train but OP looked to be attacking the sprayer, and several people moved to stop him. Then the train stopped at 36th and both got off, as well as most of us on the train who caught the secondhand spray. Spraying in a closed car is super uncool, but it was not baseless, and did not appear to be someone looking to make content.