do inconclusive reports lower weight?

I mean it greatly depends on what you reported them for as well as if you leaved a detailed comment on the matter. If trolls are getting creatives when it comes doing what they do. The system won't automatically know why you were reporting them.

Like say someone is following you in the jungle trying to steal your farm. Just reporting them for trolling wouldn't be enough since the system alone cannot check someone following you and more than likely needs to be manually checked!

tl;dr right upfront: This is speculation. I don't know how the system works, I can only (roughly) explain how I would do it. If you're not interested in speculation, downvote and skip it.

The key (in my hypothetical system) would be confidence. If the system has a high enough confidence that somebody did do something punishable after being reported (judging by in-game data), that person will be punished, and the reporters would have their weight increased if below maximum weight.

If the system has a high enough confidence that somebody issued a false report (judging by in-game data and report data), that person will get their report weight lowered if above zero weight.

In the entire middle area nothing happens to the reported or the reporter; unless the report data suggests the reported may be doing something under the radar, at which point there is a manual review.

So far I have not seen any evidence of Riot not going by this (again, very rough) idea, and I've seen a few posts pointing into this general direction.

So for your example, in my hypothetical system: The troll/feeder system still seems fairly bad at detecting things, which I'm certain is quantifiable to some degree, which means the system has low confidence in both directions. Could be a troll, could be not. So however rarely the system finds a definitive troll, that would roughly also be the scale of how rarely it will find a definitive false report for trolling. Or differently put: You will have to be very very blatantly trolling to get punished, and you will have to be very very blatantly false reporting to get your report weight lowered.

Hope that somewhat helped.

Why the hell downvote a question? Makes no sense at all. Sometimes I feel like people just scroll down on the main menu downvoting every topic without even reading the title.

yes.