Hi, Hamlet the Dane.
First off, I am not a Riot Employee. I do not hold a title here on the League of Legends Boards.
This account is rather new due to having been banned on my old account recently. I am just trying to help share my knowledge with you so that you can understand from someone who has been down that road what the aim and goal of the punishment system is to accomplish.
I read your post and I sympathize with you. I will try to give you a contextual answer based on what I have learned over the years through talking with support.
You did right by sending in a report. This players actions were both disrespectful to you and your friend, and also disrespectful to the entire game (denying either side the type of game experience they queued up to play for). However, in these types of settings (virtual intellectual property containing a virtual world with virtual currency purchased with real currency to be transferred), there is a very strict set of rules that a company on the virtual frontier must follow if they wish to conduct their business within acceptable boundaries of the law as written by congress.
That said, they cannot step those boundaries, they must go through due process unless a critical situation forces their hand to overstep those boundaries and limitations. As a means of a verifying undeniable that disciplinary action must be taking, they have decided to allow all members the chance to get a warning about their behavior.
(Don't bother reading the whole quote, focus the emboldened text)
From Section 2 of the Terms of Use (Legally binding contract that must be agreed to before being authorized to use League of Legends).
ACCOUNT TERMINATION
2.1. How can my account be suspended or terminated? (If you break the rules, Demacian Justice will be visited upon your account!)
Three different people/entities can suspend or terminate your account:
2.1.1. You. You may terminate or suspend your account at any time by contacting us at [email protected].
2.1.2. Us.We may terminate or suspend your account if we determine, in our sole discretion, that:
(a) you have violated any part of this Agreement;
(b) we have stopped offering the Riot Services in your region; or
(c) doing so would be in the best interests of our community, the Riot Services, or the rights of a third party.
We may make such determinations, among other ways, by using automated systems and machine learning tools.
2.1.3. The Tribunal®. The Tribunal® system allows our community of users to police the compliance of other users with the “Summoner’s Code,” which outlines the principles of ideal game play behavior, as well as with our other policies. Community members, including you, may submit descriptions of activity and actions of certain users within the Game, and collectively determine if that particular user was in compliance with our policies. If The Tribunal determines, in its sole discretion, that you have violated one of our policies, we may suspend or terminate your account on behalf of the community.
2.2. What happens if my account is terminated? (No LoL for you.)
If your account is terminated, you’ll no longer have access to it, including any of the associated data or content (e.g., champions, skins, Riot Points, etc.). You’ll not be entitled to any refunds and we’ll have no liability to you. We also reserve the right to terminate any other accounts you may have created (also without any refunds or liability to you).
You understand and agree that using the Riot Services comes with the risk that your account may be terminated or suspended and that, whenever you use the Riot Services, you’ll bear this risk in mind and always conduct yourself appropriately.
Due to the wording of this legally binding contract, and due to the way account suspension works (complete denial of access and revocation of authorized access to League of Legends), Riot, by conducting business and taking money as payment for virtual online goods that are not necessarily within a player's ownership, Riot Games risks the possibility of a legal suite, has since the day they launched the "Store".
The player you speak of in your post is likely being reviewed now (especially if you or your friend reported their activity). I notice that the player has a Legendary skin.
Would Riot just instantly ban that person (completely and instantly denying authorized access for that account), then the potential for a legal suit will exist as any number of reasons or excuses could be used in the party's defense. The outcome of a suit like this is not what is important, merely the existence of the suit itself is enough to put Riot Games under legal scrutiny by the public. A lot of banned players have complained of losing lots of money to a banned account, and could argue about emotional damages and whatnot. I myself poured over $3,000 dollars into my old account and it got banned, and there are likely others who have paid more (for things like unavailable skin codes at conventions that needed to be paid for to enter to receive), and are going to want to try to get money out of a case.
To protect itself from even the threat of these incidents becoming reality, Riot Games, through support, conduct investigations thoroughly into the history of a player, keeping a e-folio of documented incidents. The e-folios sometimes get very little content filling them up over time, and sometimes the judgement is made to not punish the player if it is every so often and nothing more. But a player with a long history of occasionally justified reports stacking up will likely be restricted from access once they escalate through the system. On the other hand, a player who performs key actions in a game consistently in a short amount of time (chat or otherwise) may receive a suspension much faster.
TL:DR
To put it simply, if that player hasn't received punishment lately and is in good standing, this is not enough to force that player to be instantly suspended or permanently banned. But this incident WILL be used later to determine if that is necessary (suspending or banning the account). With the way the Terms of Use is worded, it is against their best interest to ban players without a definitive confirmation that the player is a hazard to the community.
It sucks, but you're helping to make it suck less by reporting them.
Sorry you had a bad game. Best of luck. Hope this helps.