<human>: Can you condense the text into a few key points?

I talk to my friend regularly and recently she started talking about a person from our highschool that won't stop talking to her and ignoring awkward/social cues to stop. There have been instances where they met accidentally on the train and she texted me to hopefully kill the conversation between them, but he looked at the phone, ignored it and continued talking/asking questions making her uncomfortable. She has a boyfriend already and this highschool person knows it but continues anyway to talk often despite it.

I've thought about messaging him indirectly and letting him know that he's bothering my friend and she's too afraid to say it outright or block him since he 'technically didn't do anything wrong.' However I don't want to act on emotion and instead want to get more perspective first.
<bot>: Person ignoring social cues continues to talk to my friend, making her uncomfortable but she says he didn't do anything /that/ wrong. Am I stepping out of line if I intervene and is it essentially out of my hands?