I never heard of permabanning until I came to PerC.
I never got infracted, suspended, banned--nothing. And I was a mod or on staff--and asked to be on a few other forums.
One of the first bits of advice I used to give to new people who clearly needed some guidance, i.e. some said, "I'm lost here," for example, was "Never argue with a mod, just say yes even if you think no, calm down, think it through."
And "Don't come out guns blazing with someone who's been a member here (other forums) for years: Get the lay of the land.
I befriended a lot of new members because they had potential, and I didn't want them to leave for lack of support when so many stay that, well, get a lot of warnings, or know how to play the game right up to the line.
My first forum experience was in 1995, so my record of behaving well enough is long, and my intentions are usually neutral to good.
If I'm in pain, though, I gotta tread carefully, and sometimes just log off, because it can get so bad I can't tell the difference between snippy and worse--or I wouldn't if I didn't show self-control and shut the computer down until the worst pain passes.
I gotta say, from my perspective, I don't understand a ban that is not permanent, but attribute this, perhaps, to my age:
Banned in my day was a serious term, and it meant something akin to damned, i.e. don't come around here any more.