Riot-endorsed trolling methods (as learned through discussions with admins)
So, I learned several interesting things after needing to deal with admins recently for the first time since I started League about 5 years ago. Through our discussions I was able to get a better picture of how Riot's penalty system operates, and it's basically built to encourage toxic behavior. This would explain the extremely high percentage of negativity LoL is known for, but this might give you a better idea of how that has been subtly shaped by Riot's system.
For starters, apparently there are a number of hidden rules that can result in a penalty (chat restriction/etc). They are not listed on the site guidelines for reportable behavior, but apparently are flags that are used to go after an account. One example? Calling for reports. If someone gets tilted, runs down mid 5x, then ragequits and afks the rest of the game, apparently asking people to help you report them, in order to make sure an admin/the system reviews the case, is cause for YOU to get 6 months of honor reset to zero and a chat restriction. Similarly, if someone is following you around griefing you (stealing as much cs as possible, highlighting your location to the enemy with spells then running away when they rush you, etc), and you get mad at them briefly (but without breaking any specific reportable behavior like cursing, racial slurs, etc), and then mute them, yep, you guessed it, YOU are the one that gets the penalty.
Multiple admins have confirmed that it doesn't matter if they were calling you racial slurs and praising genocide, any response at all on your part other than "Why thank you for your kind words about black people, you are having a wonderful impact on the game!" can result in a penalty against you that will not be reversed. Ironically, I confirmed that the aforementioned racial slurs will NOT always result in a penalty, having had the unfortunate experience of getting matched consecutively with the same person for several games and noticed that zero action had been taken, despite his violations being blatant enough for the system to pick them up automatically even if I hadn't reported them.
So that brings me to the title of the post. As I learned, if you bait someone into saying anything negative by saying or doing something not directly reportable (non-obvious griefing to anyone but the person you're trolling), commenting things like "good job!" whenever they screw up and/or get killed, etc. Once they respond, even if it's just to say they're muting you or asking people to report you for your actions, you can report them, get them penalized with 6+ months of work reset in honor, and get away completely free. Rest assured when they contest the penalty, Riot admins will support your actions, and tell them that the penalty against them is "correctly placed". Your successful trolling will then have the added bonus of Riot's seal of approval, as they tell your victim to try and be more positive in the future, and ask them to reform their ways.
In another twist of irony, Riot's policy on this has successfully "reformed" me from a player that would try to follow the rules and keep myself within reasonable bounds when being frustrated by toxic players, to someone that realizes that such things will get you penalized anyway, and therefore plans on manipulating their rules as they were manipulated against me. As they say, you either quit LoL a reasonable player, or play long enough for Riot to turn you into the villain.
While I don't advocate trolling people that don't deserve it, and certainly don't intend to do so myself, this method of trolling/griefing has been endorsed indirectly by multiple Riot admins based on their responses to my questions. So rather than trying to confront someone about their in-game behavior (like a reasonable person would), simply troll them in this method rather than risk action on your own account. I personally find it an abhorrent policy, but it's Riot's rules, so I guess we have to abide by them.