Those bans and how much it takes to actually get a ban should be more open information.
I'm guessing that wishing death to somebody is the only thing that can lead you to an instant ban but if you insult somebody, you get some sort of warning. Add enough warnings up and you can get a ban for that as well.
I agree with you that we should make it more clear. You can find some info at this post (B-8)
You guessed right. There's no tolerance to/with that kind of comment and it gets an instant ban, while other offenses are dealt with PM's, warnings and infractions. I hope I could clear something.