The good doctor is right, it's more difficult for the system to detect trolling. Currently, the Instant Feedback System functions like a chat-bot. Reports are submitted, and it scans through the chat logs to verify whether they are legitimate or not. But with trolling, there are no verbal cues that can be detected.
Riot has been working on expanding the system to be able to detect trolling, but they are trying to make sure that it doesn't punish people for having bad games, or for simply being inexperienced, so it will take some time for that to be ready.
In the mean time, when people troll you, be sure that you report them for it. Take the time to fill in the additional comments during the report screen. While it does take more reports for them to be manually reviewed than a person being reported for toxicity would need to be punished by the system, it makes it that much more important that you actually take the time to report them. So many times people get frustrated and think "why bother reporting them, they won't get punished anyway?" and then never report them. Of course the person will never be punished if they are never reported. But if enough people report a player for their actions, they _**will **_end up being reviewed and/or punished for it if they are trolling.