to ban Dunkey or to ban the malphite?

This isn't a choice. they both exhibited behavior that goes against the summoner's code. They both deserve to be punished.

However, there is a accurate system in place for banning verbal abuse. It's a automated system that filters out key words and is very effective at discovering strings of insulting text. There is not an accurate system of banning intentional feeding.

If you know a sure fire way to tell the difference between someone who is intentionally feeding and someone who is not very good at the game then, raise your hands cause Riot wants to hire you. Think very carefully because if you put forth an imperfect model then you are banning hundreds of people every day for not being good at this game. What is a more sure fire way to kill the longevity of a game then by getting rid of all players who are trying to learn it. Don't tell riot decide by a case by case basis. Do you have any idea how many people play league of legends every day? They would have to subcontract everyone in the state of Nebraska just to get through all the games in the US. and then there is the data available. A the moment Riot is only able to save the chat logs from inside the game. In order to truly tell if a player is intentionally feeding someone has to see it and that won't happen because riot has no effective way to save game data. the first reason is it's too big. the sheer number of games played daily, combined with the total size would slow down riot's servers tremendously. Do you want to go back to 100 ping? DO YOU? If you have baron replay then you know the second reason. It's because of the patches. Every patch works differently, in order to replay a match from 2 weeks ago you need the specific patch. Riot has been patching this game every 2 weeks do you know how many patches they have to store just so they can investigate a cold case of intentionally feeding? This is the main reason why riot doesn't have it's own replay system currently. They are trying to make it so that the replay system can replay a game from any patch.

This is a flaw in the system, a big one. Riot acknowledges this flaw, and are working on a sure fire solution. It seems like they are pining their hopes on a revamped tribunal system. here is what i've heard about it.

It will include both pre and post game chat logs. the honors system will tie into this. So you can get "reported" for being a good team mate, nice, worthy opponent, or a toxic trash bag. When the case reaches the tribunal the playerbase gets to decide whether the report was valid and reward or punish the defendant properly. they want to include this because in the old tribunal people always went in with assumed guilt.

It's like how a lot a murderers got away with their crimes until DNA testing became so accurate, but since we don't save the chat logs we can only punish try murderers after DNA testing developed.