The only time telling another player "Kill yourself" would be acceptable (Brief example)
"FUCK, I'm stuck in the enemy jungle and they're coming for me" "Dude, kill yourself on a turret so they get no gold" "Good idea !!" (Ally has been executed) "Nice dude, it's great that you killed yourself" "I know right?" [bromance intensifies]
runs under turret
20 seconds later
Every time I ult my friend, but he doesn't quite die
"Go kill yourself, you'll be revived with 1.5k hp"

Where are you going?