"Feeding" is not an insult
If you by chance don't now normal video game terminology, and find it offensive when someone points out the fact you are feeding, then you need to go onto google and search up all the terms you're unfamiliar with for such games.
Examples of phrases that are by no means toxic or reportable, "bot is feeding," "the enemy bot lane is fed" "our top laner fed the enemy's" "the jungler has fed a lane"
There is only one objective meaning to these words: someone was killed by an enemy multiple times.
Any assumption that this implies harassment is completely subjective, and not admissible as reason to report a player. You are responsible for any emotions that arise from your incorrect interpretation of clear gaming terms. It also makes you look like a pansy when you whine about it.
Edit: To address the counterargument that it's harassment if it's used that way: no, it is not. Even if used in conjunction with other things, like, "wow, you should uninstall the game and kys," then the mention that they fed is still not the part that is harassment. If a player is mentioning k/d/a in an attempt to hurt someone's feelings, then it's most likely other things they say will in fact be against the rules. But simply mentioning it is by no means harassment. And here's the nail in the coffin as proof that it doesn't just become harassment because you feel it is: https://support.riotgames.com/hc/en-us/articles/201752884-Reporting-a-Player "2) DO NOT REPORT A SUMMONER FOR USING STRONG BUT NON-DEROGATORY TERMS TO EMPHASIZE AN EVENT IN THE GAME" The example given is, "that tower fucked my harder than the entire Demacian navy."
Repeating the fact does not make it derogatory. Additional words may be derogatory, like if you add to it by saying, "you fucking suck at Tristana, how did you feed an adc Darius?" But "Tristana fed Darius," is not. Riot removed the Spam report a while ago, so even spamming dragon's respawn timer when your jungler missed the smite is not harassment. Even if your jungler thinks it is.