How does this system handle trolls?

I get that it was a frustrating experience. We all get frustrated when plays don't go how we plan them. Keep in mind, though, that unless he agreed to do it, he isn't really obligated to - or even if he did, if he pinged you to back off or left the lane/fight, that's his right as a player. Unfortunately, there is no way in League of Legends to put random people together and have one be a "captain", i.e. someone whose shotcalls are obligated for other teammates. That would be unfair to the other teammates who may have their own ideas as to what is to be done.

If another player is not communicating, that's their right. I hate it too - but Riot has stated that unless someone is attempting to do something contrary to enforced rules, they are not obligated to communicate. The "enforced rules" are that in draft pick you play your assigned lane, and indirectly that junglers take smite (and a jungle item, enforced by experience penalty) and that supports take support item and don't take too much CS (enforced by support item gold penalty from over-CSing). Beyond that, players can make their own decisions, and they don't have to defend/argue them with you just because you disagree.

That's basically what I'm saying. Again, unless you saying it serves a legitimate purpose (such as my example: telling a teammate something such as "if he is trolling he won't help you so play safe" or similar), then it is not acceptable at all. The Summoner's Code defines acceptable behaviors in League, of which making accusations against a teammate violates rules 1 and 3 (among others in a more minor way). Making accusations against another player of trolling is not only not supporting your team, it's actively doing the opposite - alienating a team member. And using chat solely for ragging on someone else repeatedly is certainly not civil discussion.

Again, and I'd like you to seriously consider this, either they were trolling or they weren't. If they were trolling, your response is giving them what they want. Put another way, you responding to the troll is validating what they're doing. People troll on the internet (in games, on forums, etc) because they enjoy seeing other people get angry/enraged/annoyed with their actions. You flaming them for their actions gives that person what they want. And if the player wasn't trolling, you've now just alienated a team member and made them feel like shit, and likely shut off any chance of them coming back from that mistake.

Moving on, you certainly are permitted to have a civil discussion about why you don't agree with someone else. A civil response would be something such as "if you come to my lane, I won't help you", or "please don't gank my lane". It is not repeatedly bringing up past actions, making accusations of trolling behavior, and not really at all saying anything constructive. There is no "tiptoe" involved - you simply are not permitted to use chat to tear other people down accusing them of griefing. See the paragraph immediately above this - either you're "feeding the troll" (which is bad and should be punished) or you're tearing down a legitimate player (which ruins the game for them and your teammates by causing a breakdown in communication and should be punished). Even if other players started the accusations/flaming of this person, it does not make it okay for you to engage in it, continue it, or be a part of it. Other players violating the rules doesn't make it okay for you to.

I certainly respect your opinion that the context should matter, but I personally disagree. More importantly, data from player reports, and the Tribunal, show that the vast majority of players don't care who started it, or what else was going on. The Tribunal was a way players without recent/active punishments could "vote" on other player's chat logs and game stats to say "punish" or "not punish". Riot found that when they compared logs that had different levels of "context" (i.e. anywhere from random flaming for no reason at all to other players hard feeding or flaming first), players tended to vote similarly. Put another way, the context of the game, even though it was presented, didn't change the outcome of the players' opinions except in very very limited circumstances - well beyond your standard "troll" or "flamer". This is what led to the "lack of context" in report evaluation today - it's what most players want.

Let's say I'm a third player in this game. I see the actions you're frustrated with myself and can make my own determination as to whether I should report him. Let's assume I agree with you, it was trolling, and I decide to report. But then I see you feeding the troll - which to me is likely to result in the troll continuing to troll and not doing anything useful for the team communication. Furthermore, your bickering/back-and-forth is likely preventing me and other teammates from communicating with you or each other effectively - because the chat is broken up and busy with your flaming. You best bet I'm going to report that - while the other player may have done their bad thing "first", yours didn't do anything to help the situation and made my game experience worse. Instead of having to deal with a troll on my team, now I have to deal with a troll and someone else who's not doing anything helpful. And if I disagree and don't think the player was a troll? Well now I get to sit here and watch one teammate tear another down for what I think is no reason. So you best bet I'm reporting you regardless if I agree or not. This coincides with what Riot has said before: most reported players for chat offenses end up getting reported by players other than those they are flaming/arguing with in the game.

I'll end by saying this: if this is what you call an attempt to "communicate" in "good faith", then it's clear that you need the punishment to encourage you to change that attitude. This is barely communication - I'd go so far as to say there is no information exchange in these logs that is useful to the game, and so it's not communication. Furthermore, the primary purpose of most of the snippets of chat is to tear someone down, make them feel bad for a mistake, and attempt to bully them into doing what you want them to do. That is not "in good faith" at all.