Ways to get permabanned "by accident"
Hey there, me again to provide some info you might've missed.
There were wavebans for custom skins because some of custom skin software could be used to cheat(timers/camera). https://boards.na.leagueoflegends.com/en/c/gameplay-balance/hrqUOmAM-i-got-perma-banned-over-using-custom-skins
There is an IFS system which is not exactly obvious thing for many cultures and does not interact correctly with the ladder punishment system. https://boards.na.leagueoflegends.com/en/c/player-behavior-moderation/ALsKWJcs-did-i-seriously-get-banned-for-this
There is a chance to get banned for no reason at all and get told to go fuck yourself, because they have evidence of you cheating, even though you never cheated. Good luck causing forum uproar in that case, because you are not getting your account back in this case by writing to support. https://boards.na.leagueoflegends.com/en/c/tips-tricks/RE7XxFM8-dont-use-this-sion-ult-mechanic-or-youll-get-banned
You can get locked because you travel and fail to prove that you are an account owner, because proving that you created the seasoned account is virtually impossible, without writing everything down a lot of information on account creation. https://boards.na.leagueoflegends.com/en/c/player-behavior-moderation/wnGjqtEd-did-i-really-deserve-to-get-perma-suspended-i-genuinely-dont-get-it-i-want-your-opinions
You can get hacked due to lacking sufficient computer skills or getting new undetectable malware on your PC https://boards.na.leagueoflegends.com/en/c/player-behavior-moderation/EMAPTKbo-my-account-got-hacked-and-permabanned
Maybe it does happen by accident. Maybe you can't easily protect yourself from losing your account in any situation.
And Riot reserves the right to ban your account for no reason in addition to that.