Correct, it is not ONLY player reports. Player reports get the name, server, date/time, and logs in front of a GM. The GM decides if the reports are valid and issues a penalty, or not, based on the logs.
There is no automated system behind a suspension though. That was applied by a human looking at reports and logs.
If you keep getting reported it means that your fellow team mates don’t consider your play style to be helpful participation. To get a suspension it means you were reported over multiple games and the logs backed low participation.
The goal is to keep people from “leaching” by just running off somewhere and hanging out instead of helping the team actively.
Leilleath correctly posted lots of Blue Blizzard posts on the subject.