From Riot's support knowledgebase:
It only takes one report for our systems to review a game.
LoL's Honor system rewards you with things like Honor, BE, and key fragments when it deems your behavior good. LoL's punishment system (the IFS, or Instant Feedback System) places a punishment on your account when it deems your behavior bad. Behaving well sometimes doesn't mean you behave well all the time. In this instance - and possibly others, since the IFS punishes based on severity and consistency, and the reform card doesn't necessarily display logs for every match where you were validly reported - you behaved poorly. Poor behavior is very impactful and thus carries a lot of weight with the IFS, so to regain Honor and avoid losing it you'll have to work on controlling your behavior. The IFS does forgive the occasional bad day, but if that kind of behavior becomes habitual, you might be greeted with a reform card telling you to rein it in, or with a permaban message if the temporary punishments haven't worked.
You weren't punished for misbehaving in one game. You were punished for misbehaving in one more game, in a consistent pattern of negative behavior that breaks the game's rules. Additionally, the reform card doesn't always show all the logs that led to your punishment: it randomly selects up to several logs. You might see three logs, but you also might see as few as one, even for players whose punishment stems not from a small number of egregious infractions but rather from dozens of instances of mild toxicity. The purpose of the reform card is to tell you how to reform, so it shows you an example of the behavior that prompted your punishment and explains that such behavior is inappropriate and should be avoided if you want to maintain an account in good standing.
In a perfect and just world, everyone who deserved a punishment would get one. In reality, it is possible for some punishable behavior to go unpunished. First, punishments in LoL can only occur after a valid report. Second, punishments take into account the consistency and severity of the punished player's misbehavior: if two players in a match break the same rule in the same way, one who consistently misbehaves in this way might get a punishment while the other who almost never does so gets away without a punishment (this time). At the end of the day, though, all this does is explain how differences in player behavior over many games can produce different results for equivalent behavior within a single game. It doesn't excuse poor behavior. One person having a rare bad day doesn't give a consistently toxic player the right to join in. The only behavior that matters in your punishment is your own... and a good thing, too: how would you feel if you behaved yourself but got punished anyway just because all your teammates were spectacularly friendly, communicative, and positive?
From Riot's support knowledgebase:
We can not discuss other players’ actions with you but you can always report them at end of game and mute them when in game. There is no excuse for raging back or responding to people trying to get you to tilt. You are the only one responsible for your actions and your words which is what we are trying to address with these bans.
