My opinion, after years of playing and after being in this forum for a ~week now and seeing the current situation.
Immediately increase the difference between the punishments for extreme toxicity and regular "banter".
It's absolutely disgraceful, that racism and death threats get you permanently banned for 2 offences, while mild negative attitude can get you permanently banned for just few more offences. There should absolutely be a bigger gap between these two. Just increase the chat restriction punishments maybe? If they have been used for years now, I assume Riots stats sho they tend to help. I've seen many people here not agree with it, I personally do agree. At least someone who was usually punished for negative attitude, when I got tilted, chat restriction definately helped me focus more on the game than on the chat.
I also don't really agree with the fact that this would ruin your teammates games somehow, if you think about your soloq games, how much of the text in chat is actually helpful/about teamwork and trying to win? You can use pings for anything immediate/important. It's not like its usual that players are writing out some long strategies in the chat.
Overall I wouldn't mind the current punishments for extreme verbal offences, one warning should be enough before a permanent ban, if you tell people to kill themselves or something similar. I do think that punishing for mild stuff has crossed the line, in a game that has built-in chat filter and the possibility to mute someone with one mouse click, I don't agree that negative attitude (which is so usual in team sports) should be punished that severely.
Definately change the way intentional feeding bans are being handled. I'm not sure how actively the support team is looking over unban appeals, if they are doing it, this might not be that big of a problem, but otherwise I see a huge issue with banning people for intentionally feeding just from their scoreline/builds/cs per minute or which ever stats. In normal games you can duo with whoever, so if a beginner duos with a diamond player, and gets to play against a gold for example, they could absolutely without any negative itention go 0/20, even if they really try to play defensive. And this could easily happen several games in a row. Since you cannot duo like this in ranked, it would make sense to have this kind of automatic detection in ranked, not in normal
Also griefing. I have been banned from the game, but I can say I have never griefed/ran it down. I still think situatsion like the kindred player case ( https://streamable.com/j68wk ) should definately not be punished, at least that harshly. I play in similar skill level to his, and I see so often plays like that. Sure, it might come from being tilted and not focusing enough, but this to me feels nothing more than banning people for playing bad. Especially playing at night, I see these kind of things so often, someone is tired, decides to play one more game - finds out they shouldn't, because they are actually too tired - maybe getting autofilled aswell - what happens is they play wayyyy below their skill level. Sure they have maybe ruined someones game, but the average ranked player plays what, 400-500 games a year? Should someone be banned for playing really bad in one game? Makes no sense to me.
Cheating? Permanent ban for first offence, I don't mind. As long as it's obvious/proven of course.