The scoring system is based off of kill participation. Assists only count for a small percentage because in a team fight you could get 4 assists on one team with one kill, and do that 5 times. Assists v deaths is rather heavily weighted statistically towards deaths as far as scoring goes. However, a support with the same score and even 2 kills will probably bump up to s-.
Supports getting kills isn't terribly bad since an adc still gets assist gold, still has ALL the cs anyways which accounts for a hefty amount of their gold income anyways and certain supports like Morgana, Zyra, Blitz and Sona can carry games just as well as anyone if they have the gold income behind them. I don't fret about 2 kills stolen in a game. Yasuos and Vaynes get their egos hurt, but that's their problem.
Great example was last night as Morg support. My adc was doing reasonably well and yasuo roamed bot to help us under enemy tower. He got the support and the adc was trying to escape at like 8% hp. I throw a q to stop their escape and nail them for an accidental kill. Yasuo was there a moment too late. He was upset, but let it go. As support, that kill would have been better placed on the yasuo, but the core point is the adc was dead for 15 seconds in which we owned the lane. Yes, his k/d/a isn't inflated, but we're just as much closer to winning AND I had some gold to finish another item. We all know a morg with FQC and Zhonya's is a bitch in a teamfight. THat extra gold to get my core items was a force multiplier.
TL;DR Getting kills as a support isn't a big deal. The only reason people say it matters is because they think k/d/a matters in an objective game. That said, don't KS if you don't have to.
EDIT: I had a similar Nami game that was 3/8/34 or something like that and I got an s-, but we STILL lost. That burned me so bad lol
mains we can do flashy stuff too), etc. etc. yet I was only awarded an A?
and stole a bunch of kills just to troll the ADC I was duoing with, and yet that undeniably awful support behavior is rewarded???
for the first time 2 days ago, went 13/6/15, and scored an S+.
