So i have to reform, but i found myself asking "Is Riot really whishing that i'll succeed in the process to reform? "
If they didn't wish you'd successfully reform, they wouldn't have given you the chance to. You'd have been flat-out permanently banned. The fact that you weren't should stand as evidence enough that Riot wishes for you to reform, especially since you were punished for intentionally feeding, a behavior that pretty much the entire community takes seriously.
I have an alt account, even more than one and i'm thinking to leave my banned account and starting with another, so i can be honored, take chest and so on...
That is an option, but I fail to see what benefit that confers to you, particularly if you don't play those alt accounts as much as your recently-banned one.
...and i am not encouraged to get better behaviour on other acc.
You're encouraged to get better behavior on the punished account (any account you hold, for that matter) by the Honor system, and discouraged from continuing with the poor behavior by the IFS. 'Cause you know it'll punish you if you don't improve.
I see no alternatives for my temporarily banned account ecept "mute all"...
If you intentionally fed in response to other people's chat, then yes, /muteall would be a valid and useful tool. Even beyond that, though, you do still have options, like practicing breathing exercises and building up some degree of tolerance to other people's chat.
Regardless of what avenue you pursue in that regard, remember that the best way to deal with flamers or people who frustrate you in a match is to mute, report, and move on.
...and hoping that the ban system will not detect a false positive...
False-positives are rare. If you're worried about the system "detecting a false-positive", I think you should be more concerned with why your behavior would trigger a punishment - 'cause if it looks like misbehavior, sounds like misbehavior, and feels like misbehavior, odds are pretty high that it's misbehavior.
...meanwhile nobody from Riot to playerbase ecourage me to reform, by rewards, guides, or any kind of whatever appropriate helps.
Riot does encourage you to reform. The Honor system exists to reward you for maintaining good behavior throughout your League career, and that extends to reforming from a punishment. Beyond that, what rewards do you really want? You can't expect Riot to give you extraneous things to incentivize you to prove you can be better. And besides, even if they did layer on extra rewards for reforming, you've already shown an eagerness to ditch the account you got punished on and switch over to an alt, because "you wouldn't be losing anything in (that) trade"...
As for guides, it's impossible to make anything resembling a reliable guide to reforming, because everyone is different, their situations are different, and how they go about changing their behavior will universally be different. I manage to get by well enough checking my anger through breathing exercises and occasionally slamming my table, but who's to say those small venting tricks would work for you?
Reform and change are a personal thing. And let me tell you, it doesn't matter if the whole world would encourage you to reform, all that encouragement doesn't matter if you don't actually want to do it. Reform is something you have to want to do, not something that you should be encouraged to do. My grandma always used to tell me "No-one can change you but you", and I'd say that rings truer than any idiom you could find about change and reform.
So, allow me to offer my little bit of encouragement; you should reform, not because you have anything to lose for not doing so, but because you should be able to invest in your accounts with confidence instead of readily discarding them as soon as they get punished for breaking the rules. If you don't care for any individual account enough to reform for them, then it's down to time alone to see just how many accounts you play on, ditch, and ignore because you feel like there's no point in reforming.
So ditch the pessimism, knuckle down, and put forward the effort to get your account into a stable position. Riot's giving you a chance, so you should take it. But whether you do or not is entirely up to you.
The process to reform is left to the banned player in a situation when an insignificant or minimal thing could proc the perma ban. Am i wrong?
You are mistaken, but not necessarily wrong.
Gameplay and chat punishments are two separate tracks, so you're only at risk of being permanently banned if you intentionally feed or troll again after your suspension is up. Your chat punishment track remains at wherever it was before the 14-day ban - whether that be a blank slate or a 14-day ban as well is up to your behavioral history.
If you had worked your way up to a 14-day ban through chat-related misbehavior, then a minor instance of negativity or inflammatory chat may well push you into the permanent ban, but don't confuse that for "insignificant/minimal" things. The IFS punishes for needless and excessive negativity or inflammatory chat behavior, so to get punished for it, you'd have to be disruptive to the game through negativity or flaming.
And it's also a "straw that broke the camel's back" scenario. Reaching a 14-day ban through chat misbehavior typically is a result of consistent misbehavior across a good while of play. You'd have to get a 10-game Chat Restriction and 25-game Chat Restriction before getting the 14-day ban, and the build-up to each individual punishment generally tends to take time, unless you're a rampant flamer who disregards the rules.
And all of that time and build-up means a lot of games where other players were left frustrated and annoyed with consistent negativity and/or flaming, and with that kind of behavioral history and affect on the community in mind, it makes sense that reaching a 14-day ban through chat misbehavior would result in a scenario where even a smaller infraction could lead straight into the final penalty.
But, even with all that said, I do want to reiterate that, because you were punished for intentionally feeding, you only need worry about a permanent ban if you go straight back to intentionally feeding after the ban clears. Gameplay and chat punishments are separate, so as long as you don't repeat the same mistakes, you do have a fair amount of leeway into reforming.
