Well, one thing thats important to note is that how Riot intends their system to work doesn't always match the reality of it. I'm sure this board believes trolling is an automatic two week ban, but that isn't the case. I highly doubt the people here who defend Riots system have ever actually been punished by it, therefore their understanding of how it works only consists of how Riot wants them to believe it works.
Trolling is often subjective. An automated system cannot detect trolling. If someone is trolling in the way the OP described, they are not getting banned. Thats just the reality of having an automated system and Riot very rarely manually reviewing games.
The reason I could tell Gakupo has a poor understanding of the system is from the fact that he thinks because there are a handful of people who have been banned for trolling on these boards, that means they "WILL/HAVE" gotten caught. Compare that to the thousands of people who troll/int every single day, and you can see its very likely they aren't getting caught. Have you ever seen those 0% winrate Tahm Kench smurfs that troll in Bronze 5 for hundreds of games?
Maybe I shouldn't have said "they don't get caught", but rather "99% of the time they don't get caught".