Young "man" and young woman kissing. He seems just a bit more eager than she is, judging from her facial expression.
Young male puts his hand partially around young woman's throat.
I look at them - especially the male - pointedly and ask "Is there a problem?"
It's likely that he's trying to hurt or coerce her - but not a sure thing. All I know is what I've seen in the last couple of minutes. So I don't make accusations I can't prove.
What I'm doing is letting him know that someone else - who may be willing and able to intervene in some way - is watching, and doesn't necessarily approve.
Young man removes his hand from her throat. They begin kissing again, and she doesn't (seem to) feel anxious any more. Things seem better, at least until I get off the train.
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