I think we found evidence that Riot doesn't punish inting...
Just played a game with a guy who told us he was running an experiment with this account to see if Riot actually punished trolling/inting. He said this in lobby to give us a chance to dodge, which no one did. I respect the warning.
His match history of 44 games? Most recent: 1-19, 1-16, 0-10, 0-12, 0-23, 1-9, 4-19, 1-19, 0-18. You get the idea. Of course, when we got into the game, he immediately began running it down. Kind of fun to watch, he was playing like a bot of some kind. Throwing ults at no one, tanking towers. He was a support, but went midlane to steal farm (died almost immediately - twice), then went bot and continued to die. Very obvious things like walking past creeps into tower range to attack two full-health enemies at level 2, etc.
His match history is impressive in the consistency of his losing and feeding. He said he started the experiment a month ago in Flex Ranked, he assumes people are reporting him, but so far nothing from Riot after 44 games - and even despite the fact that he admits the behavior in lobby before the game begins. So, it's about as clear cut of a case that I think can ever exist.
I have to think that if this guy can have 44 games of straight up, confessed, inting behavior and not be punished, no one will ever be punished.