When a player threatens to leave for whatever reason and I happen to have chat on, I'll likely tell them something along the lines of 'fine, cya'.
I'm not going to pretend like they're my special friend just to get them to keep on playing. I'm not their pappa, their momma, their encouraging big bro or sis. I'm a total stranger to them same as they are to me. They want to quit? They want to troll? They want to intentionally feed? Nothing I can do to stop them and I won't even bother asking them. It's their choice whether they want to play by the rules; otherwise, they can fuck off for all I care.
And if this edited post somehow still violates board rules, Riot, then fuck it. I'll sit quietly in my corner with my mouth shut like a good boy.