Punishment (the concept)
https://link.springer.com/content/pdf/10.3758/BF03342351.pdf
The link shows a couple things. First, punishment is not a cure. Second, consistent and timely punishment is necessary or else relapse occurs. If League of Legends is to be a toxic-free environment, it is going to take more than just a punishment system. Especially relevant to this forums where it is a common sight to see requests for punishment.
Relevant to the "reform experiment" as well. Punishment alone is not going to be super effective at "reform". While I think it is great to experiment with reform, the "threat of punishment" strategy has already been tried. That is what got them into the "perma-banned" status to begin with. Try something other than "behave or we will punish you (again)".
Since punishment is a temporary behavior modifier, is tier-based escalating punishments beneficial? My hypothesis is that the repeated issuance of punishment is responsible for "reform". The severity of punishment may affect time between relapse.