In the past 2 days this has happened twice in my games. One on the enemy team and one just now on my team. It seems ridiculous to me that if someone dies once and quits the game at 4 minutes then doesn't come back for the rest of the game, the team they left basically automatically loses LP for nothing and they get a 5 minute queue ban or something stupid.
We had to agree as the 4 of us to open up mid, and even leash them on the rift herald and run back into base with the enemy team and watch/dance along as they ended our 10 minutes of suffering for -18LP, (which was pretty funny at the time thinking about it) but we shouldn't have to lose our LP just because 1 minute after the remake timer someone leaves for the rest of the game especially when they get a little slap on the wrist and they can go again.
I have no idea how this could be combatted other than some sort of tweaked abandon feature like in Dota but adapted to how League works.
(Yes, I'm salty)