I don't mod a default, but in my experience it's historically been really easy to get someone shadowbanned for self-promotion by submitting to r/spam. I don't know if it's run by a script or just overworked interns, but anyone technically breaking the 20% rule over any period of time has tended to get the axe without consideration of mitigating factors (celebrity, posting to subs that encourage self-promotion, etc).

I don't know if that's changing with the drama over r/gamedeals company reps being repeatedly shadowbanned for trolls submitting them to r/spam, but not optimistic.