Back in 2015 I was banned by Riot, this was later posted by Riot Lyte:
Just wanted to jump in here with an immediate update. The Instant Feedback System had an issue on just the EU West Server for the last few hours--due to a human error accidentally changing the numbers in the system, the system banned players and sent them neutral chat logs when the bans were undeserved. We're in the process of unbanning the players as we speak, and we should have the issue resolved in a few hours.
This a huge blunder on our part, and the team is going to reach out personally to the players that were impacted over the next few days once we resolve the issue. We'll post updates here when we have them.
UPDATE ::: All undeserved bans have been reversed. We'll be sending a personal mail from myself and the team to those affected tomorrow to let them know what happened.
Today the system is just as bad, people are getting banned for reasons such as saying "fak" when they die, and it is really to just play on a premade team and report a player for such a thing, and then get player banned. Back in 2015 they also used alot of time before unbanning me, and I almost had to zone all the 14 days full out.
Also, when I sent them a ticket back then, the only answer I got was "read the summoner guide". "next time you will get permbanned". The fact that the Riot Support doesn't actually listen to you, and most of the times just send copy pasted messages back to you is just disgusting.