I understand why I got punished, but taking in consideration my history - during 6 years of playing on this account i didn't recive any suspension, temp. bans and recived maybe 1 chat restriction - I think punishment should't be so hard.
Previous good behavior isn't supposed to mitigate the severity of punishments - especially not those for zero-tolerance behavior. Your past good behavior should only matter in regards to your punishment insofar as it sets the standard of behavior that's expected of you.
Like 97% of my games I'm not toxic at all and phrases I got suspended for were written under impulse (ally has slain an enemy killing which would give me Pentakill).
In all those six years, you've never, not once acted out on impulse like that before?
So why'd you start now?
Is there any way my punishment can be softened?
No. You broke the rules, and in an especially egregious way at that. You told someone to end their lives over a videogame. You should accept the 14-day ban, and take that time to contemplate the gravity of your offense, and compare it to your previous history of good (or at least acceptable) behavior, and think about how you're going to compose yourself going forward.