Riot doesnt care, ive reported a youtube channel that actively sells cheating mods and livestreams hacking to them more than a month ago. The channel is still up, with more than 14k subscribers :)
They don't. I've had thousands of throwers, no commers, second half tilters, afkers, griefers reported and not once have I gotten their message about "keeping the community clean" which they usually send if you got a guy banned.