Consistency and severity
You know what they say, you shouldn't worry if you get reported often, false reports do nothing.
Well, it's true. If you are saint. Let's take a hypothetical example. I'll use concrete numbers to make example more clear but they should not be exactly that.
We have two players being mildly obnoxious. They like the phrase "stop feeding" and use it in 30% of their games.
Assuming this type of behaviour requires major consistency to get punished, let's take a 20% threshold - if you get 20% of your last 100 games reported and you say "stop feeding", you get a chat restriction to show that your behaviour is not okay.
The first player mains Tristana and is fairly decent at the game. He is an exemplary player of his rating and his performance has no glaring flaws for other people to notice. Community doesn't perceive a single instance of "stop feeding" as report-worthy and Tristana gets away with 5% of her games receiving a report. She would never reach the threshold to get punished.
The second player mains toplane Soraka. He gets reported every time he loses the ga!e plus sometimes when he loses his lane, despite the game being won, resulting in 60% games heavily skewed towards the lost games, where our player is more likely to say "stop feeding", making him very likely to reach necessary threshold, despite displaying the same behaviour as the Tristana player.
It should not necessarily be off-meta. It can potentially affect many people, like those with feminine nicknames or those who had reductions in performance due to RL difficulties or bad luck in league(talking about tilt). Sure, it won't be 5 to 60%, but even 19% to 20% is a huge difference.
Be welcome to try and justify it or prove that current punishment system relying on reports doesn't affect some groups of people more than the others for the same violations.