Players are only up for punishment if they are reported. So, if you didn't report them, and nobody else reported them, the Instant Feedback System didn't review their chat logs. The IFS is a great system, and is capable of scanning through thousands of logs in an extremely short period of time, but it doesn't work automatically. It has to have reports to be triggered. So, if a player is harassing you, or being toxic, and you feel like they are genuinely ruining the gaming experience, it's important to submit a report at the end of the match. Chances are, if the player is being extremely toxic, it's not a rare thing, and they probably have done it to other players as well. The best, and only, way to stop them is by submitting reports so that the system can issue punishments.
As far as why the chat logs are one-sided, that's because honestly.... what other players say doesn't really matter when it comes to what you specifically said or did in game. We are all responsible for our own actions, and even if another player is instigating things, that doesn't give us the right to break the rules in retaliation. In those cases, Riot simply asks that we either ignore the players, or mute them if we can't ignore them without replying, and then report them after the match. Riot doesn't ask players to have an inhuman level of self-control. They built in the ability to mute other players, and give us pings to be able to still communicate with our team if we choose to mute them. If you are having issues with a toxic teammate, I strongly recommend that you mute the player, rather than try to argue back to them, as any sort of retaliation will only end up in you being punished if they report you for it.
