Two ways to get pink here. One, rack up infractions until the system gives you an automated ban. Length of these bans vary, depending on how many current points you've racked up. The first ban is a week or so....
Second method, you spread so much chaos throughout the forum the mods decide to vote on a permanent ban. These are a last resort, and require a majority vote of moderators.
So if you've been infracted or banned, more than one moderator has had their say. If the reasons don't always seem completely obvious, it's likely because we've removed some particularly offensive or inflammatory material. We don't like deleting, but some things just can't stay in the public eye... And we generally give plenty of warning before issuing an infraction or ban, both in the threads and through PM's.
There are two ways to get instant and permanent bans without debate. One, shower the site with spam advertising. Two, get caught holding multiple accounts for either trolling purposes or trying to get around a short term ban....
Hope that adds a little clarity.