I had a race a couple of days ago (was A and A) and I got 2 penalties from tapping someone's rear bumper (both incidents harmless, nobody's races ruined, no divebombing. Have the replay saved if people want me to prove this). First was 2 secs and second was 3 secs. Second one was caused by someone parking on the final corner of Suzuka to clear their own penalty, the guy in front had to brake hard mid-corner, I reacted but tapped him - thus couldn't clear it before end as it appeared literally as I crossed the line.
I ended up with an SR of C (dropped from 75 down to 35!). Then ran a CLEAN RACE around Mount Panorama and checked, my SR was then 36... SR calc is nerfed IMO, there's no way that works.
I then ran another race around Panorama, not clean, but no penalties or anything (the main problem was a single off with no penalty) and my SR dropped to 26! I get they want to discourage bad driving, but this seems incredible. I am not an SR:S player, but I'm not a dirty driver.